Integration By Partial Fractions - By The Organic Chemistry Tutor
00:0-1 | in this video , we're going to talk about how | |
00:02 | to integrate rational functions used in partial fraction decomposition . | |
00:08 | So the first thing we want to do is make | |
00:09 | sure that this integral is completely factored on the bottom | |
00:14 | . We have a difference of perfect squares . And | |
00:17 | so we can factor that expression by taking the square | |
00:20 | root of X squared which is X . and the | |
00:22 | square root of four which is to one is going | |
00:25 | to be positive to the other will be negative too | |
00:29 | . So what we have on the bottom is two | |
00:32 | distinct linear factors . Now you might be wondering what | |
00:36 | is the difference between a linear factor and a quadratic | |
00:42 | factor ? Linear factors include examples such as X three | |
00:53 | XX Plus four , four X -5 . Those are | |
00:57 | linear factors quadratic factors . They typically have an X | |
01:01 | squared , so X squared X squared plus four . | |
01:06 | That's a quadratic factor , X squared plus three . | |
01:10 | Acts , that's another one or X squared plus two | |
01:13 | X plus seven . Those are quadratic factors . Now | |
01:21 | to use the technique of partial fraction decomposition , what | |
01:26 | we're going to do is we're going to break up | |
01:27 | this expression Into two smaller fractions . So here we | |
01:36 | have X plus two on the bottom , we're gonna | |
01:39 | have some constant Over X-plus two dx . And here | |
01:46 | we have another linear factor in the bottom , so | |
01:48 | we're going to have another content on top Over X | |
01:51 | -2 DX . If we had a quadratic factor , | |
01:55 | let's say , like for instance , X squared plus | |
01:58 | eight . Instead of putting a constant , like A | |
02:00 | or B . Well put a linear factor A , | |
02:04 | X plus B . Or like bx plus C . | |
02:07 | If we had a quadratic factor in the bottom . | |
02:10 | Now , just to give you an idea of what | |
02:12 | partial fraction decomposition is , let's say if we have | |
02:17 | one plus four , I mean one of the four | |
02:19 | plus 1/5 . If we wish to add these two | |
02:23 | fractions , we would need to get common denominators . | |
02:27 | If we multiply this fraction by 5/5 , it will | |
02:29 | become 5/20 . If we multiply this by 4-4 , | |
02:33 | it will become 4 20 . So the sum of | |
02:39 | these two fractions , one of the four plus one | |
02:42 | of the five , It's 9/20 . Partial fraction decomposition | |
02:50 | allows us to start With this fraction 9/20 and break | |
02:56 | it down into these two simple fractions , one of | |
03:00 | the four plus one of the five . So that's | |
03:03 | a good example of partial fraction decomposition . We can | |
03:06 | take a single fraction And break it up into two | |
03:09 | smaller fractions . It could be two or more smaller | |
03:12 | fractions , it could be three fractions , it could | |
03:14 | be four . But that's the idea behind partial fraction | |
03:18 | decomposition . We're taking a single fraction and break it | |
03:23 | up into multiple fractions . So what we need to | |
03:28 | do here is we need to determine the value of | |
03:30 | A and B . And this problem . So for | |
03:34 | now I'm going to get rid of the integral symbol | |
03:37 | and the dx term . And we're going to set | |
03:41 | this fraction equal to A Over X-plus two . Yeah | |
03:51 | , plus B Over X -2 . If we can | |
03:56 | calculate the value of A and B , then we | |
04:00 | could use that to find the indefinite integral of those | |
04:04 | two expressions . So we're going to do right now | |
04:07 | , is we're gonna multiply every term . Bye . | |
04:11 | The denominator on the left side . So that is | |
04:13 | by X-plus two And X -2 . So when multiplying | |
04:21 | this fraction by these two factors , This is going | |
04:25 | to cancel and we're gonna be left for for one | |
04:28 | on the left side of the equation . If we | |
04:31 | take A over exports to and multiply by exports to | |
04:35 | expand its too . The X-plus two factors will cancel | |
04:42 | leaving behind A times X spanish too . Now let's | |
04:55 | take this fraction multiplied by those two factors . So | |
04:59 | X minus two will cancel . And we're gonna have | |
05:02 | be times X plus two . Now , when you | |
05:12 | have linear factors like X minus two , X plus | |
05:14 | two , there's a shortcut technique that you could use | |
05:18 | in order to calculate the value of A . And | |
05:20 | B . And that is by plugging in certain X | |
05:23 | values . If we were to plug in X equals | |
05:26 | two , This term becomes zero so we're gonna have | |
05:31 | one is equal to eight times two minus two to | |
05:34 | minus 20 So this becomes zero plus B . And | |
05:38 | this is going to be two plus two , which | |
05:40 | is four . So what we have is one is | |
05:43 | equal to for me And then dividing both sides by | |
05:46 | four . We get that be Is equal to 1/4 | |
05:59 | . Now another value that we can plug in Is | |
06:02 | -2 . If we plug a negative too negative two | |
06:05 | plus two becomes zero . So this whole thing becomes | |
06:08 | zero . And so what we're gonna have is one | |
06:11 | is equal to a . Times -2 managed to and | |
06:17 | negative two minus two is negative four , Dividing both | |
06:21 | sides by -4 . We'll get that a . Is | |
06:24 | -1/4 . So now we have the values of A | |
06:29 | . And B . So going back to this expression | |
06:34 | let's replace A . With negative 1/4 and then let's | |
06:42 | replace B . With positive 1/4 . Now what we're | |
06:59 | gonna do is we're going to take these constants and | |
07:02 | move them to the front . So this is gonna | |
07:09 | be negative 1/4 integral one over X plus two dx | |
07:18 | And then plus positive one of the four integral one | |
07:21 | over X minus GDX . Now let's talk about how | |
07:26 | we can integrate rational functions . The anti derivative of | |
07:31 | one of her ex is Ellen X . Now we | |
07:37 | need to use an absolute value symbol because we can | |
07:41 | have a negative value inside a natural log function . | |
07:45 | It's not gonna work , it's gonna be undefined . | |
07:50 | So let's say if we want to integrate one over | |
07:53 | X plus five it's going to be the natural log | |
07:57 | of X plus five . If we have a constant | |
08:01 | on top of that let's say four over extra seven | |
08:06 | . This is going to be it's L . N | |
08:09 | . X plus seven . But times for now let's | |
08:14 | see if we have the anti derivative of 1/2 X | |
08:18 | plus seven . This is going to be Ellen two | |
08:23 | x plus seven but we need to take into account | |
08:27 | the two in front of the attacks , The derivative | |
08:30 | of X is one . So when you divide this | |
08:32 | by one , the answer doesn't change . The derivative | |
08:35 | of two X . is too . So we need | |
08:38 | to divide this by two . It turns out this | |
08:40 | is gonna be one half Ln two X plus seven | |
08:44 | . Likewise , if we want to find the anti | |
08:46 | derivative of 1/3 X plus eight , this is going | |
08:52 | to be Ellen do we act plus eight ? But | |
08:55 | then Divided by the derivative of three X , which | |
08:58 | is one of the three . And of course all | |
09:01 | of these have plus see the constant of integration . | |
09:06 | Now let's see if we have seven Divided by five | |
09:10 | x plus nine . So this one we have to | |
09:15 | be more careful . This is gonna be Ln five | |
09:18 | x plus nine . But we need to divide this | |
09:21 | by The derivative of five x . Which is going | |
09:25 | to be five . So it's one of the five | |
09:29 | if you're dividing it And then we have to multiply | |
09:31 | by seven . So it's time seven times 1/5 Ln | |
09:36 | five X plus nine . So you're going to be | |
09:40 | using this a lot when dealing with partial fraction integration | |
09:48 | . So I want to just give you some ideas | |
09:50 | on how to integrate rational functions into natural algorithmic functions | |
09:58 | . So the anti derivative of one over X plus | |
10:00 | two , that's simply going to be Ln exports to | |
10:06 | And the anti derivative of X -2 is going to | |
10:09 | be Ln I mean the inside derivative of one of | |
10:13 | our x minus two , S L n x minus | |
10:16 | two . Now let's add the constant of integration . | |
10:23 | Now , what I'm gonna do is I'm going to | |
10:24 | factor out one of the four and I'm going to | |
10:27 | write the positive term first in the negative term . | |
10:30 | Second , It's a factory that one of the four | |
10:34 | . We're going to get Ellen x minus two minus | |
10:41 | Ln x plus G . Now a property of logs | |
10:49 | is that we can convert to logs into a single | |
10:53 | log . For instance , let's say we have L | |
10:56 | N A minus Ln B . We can write this | |
10:59 | as Ellen A over B . Or if we have | |
11:03 | L N A plus L N B , we can | |
11:06 | write this as a single log Ln A times B | |
11:10 | . But for this problem we have a minus sign | |
11:13 | . So we're going to use that property of natural | |
11:16 | logs , which applies for all logs . So we | |
11:21 | could rewrite this answer as one of the four times | |
11:27 | Ellen absolute value . This is gonna go on top | |
11:30 | since it's positive , this is going to go on | |
11:37 | the bottom since it has a negative sign in front | |
11:40 | of it and then plus C . So this is | |
11:48 | the final answer for this problem . So that is | |
11:54 | the anti derivative of one over x squared minus four | |
11:58 | . So that's how we can get that answer . | |
12:00 | Use an integration by partial fractions . Now , let's | |
12:04 | work on a similar example for the sake of practice | |
12:07 | , so feel free to pause the video . If | |
12:09 | you want to try this example , We have the | |
12:11 | integral of X -4 over X squared plus two X | |
12:16 | minus 15 . So go ahead and try this problem | |
12:20 | . The first thing we need to do is we | |
12:22 | need to factor this expression completely , particularly the denominator | |
12:27 | and what we have is a try no meal Where | |
12:29 | the leading coefficient is one . So we need to | |
12:32 | find two numbers That multiply to the constant negative 15 | |
12:37 | but add to the middle coefficient to So this is | |
12:41 | going to be positive five and negative three . Five | |
12:46 | plus negative three adds up to two but multiplies to | |
12:49 | negative 15 . So it's a factor . This expression | |
12:53 | , It's going to be X-plus five times X minus | |
12:58 | tree . So here we have two distinct linear factors | |
13:04 | . So we can write this as the integral of | |
13:07 | a Over X-plus five dx plus the integral of B | |
13:15 | over ex monastery dx . So like last time we | |
13:19 | need to calculate the value of A and B . | |
13:22 | And then we could find the answer . So let's | |
13:29 | set this fraction equal to the two fractions that we | |
13:34 | have on the right , just without the integral symbol | |
13:38 | . So this is going to be a Over X-plus | |
13:41 | five and then plus B over X monastery . And | |
13:49 | just like before we're gonna multiply everything . Bye . | |
13:53 | And those two factors . So multiplying this fraction by | |
14:03 | X-plus five times x monastery . And these will cancel | |
14:08 | . And we're going to get X -4 on the | |
14:10 | left side of the equation . This fraction time is | |
14:17 | those two factors X-plus five will cancel . And we're | |
14:20 | gonna have a times X minus street left over . | |
14:30 | And then when we multiply be over ex monastery by | |
14:32 | these two factors , the x minus three factor will | |
14:37 | cancel . Leaving behind B times X plus five . | |
14:46 | Select before we're going to plug in X values to | |
14:49 | calculate the value of A . And B . So | |
14:51 | let's begin by plugging in three . If we plug | |
14:55 | in X equal street This term goes to zero . | |
14:59 | So we're going to have 3 -4 is equal to | |
15:03 | zero Plus A . B . Times three Plus 5 | |
15:08 | . Now 3 -4 is negative one , three plus | |
15:11 | 5 is eight , Dividing both sides by eight . | |
15:16 | We're gonna get that B is equal to negative 1/8 | |
15:24 | . So now let's go ahead and calculate A . | |
15:29 | What X . Value ? Do we need to plug | |
15:31 | in to get A . To find the X . | |
15:36 | Value ? You could set X plus five equal to | |
15:38 | zero and soft rex . If you do you get | |
15:42 | X . Is equal to negative five . So that's | |
15:46 | we're gonna plug in we're gonna plug in -5 . | |
15:51 | So this becomes negative 5 -4 is equal to a | |
15:56 | . Times -5 -3 . And then negative 5-plus 5 | |
16:02 | will become zero . But you can write it out | |
16:03 | to show your work if you want to -5 -4 | |
16:06 | is negative nine , -5 -3 is negative eight and | |
16:11 | then negative five plus 50 dividing both sides by negative | |
16:16 | . Ain't we get that ? A . Is equal | |
16:20 | to positive 9/8 . The two negative signs will cancel | |
16:26 | . So now that we have the values of A | |
16:28 | . And B . We can go ahead and plug | |
16:30 | it in into the original expression . So this becomes | |
16:36 | 9/8 and this is gonna be -1/8 . So we | |
16:54 | can rewrite this size 9/8 times the integral of one | |
17:00 | over X plus five dx And then -1/8 Times The | |
17:05 | integral of one over X minus street dx . The | |
17:12 | anti derivative of one over X plus five is going | |
17:15 | to be the natural log of X plus five . | |
17:21 | And then the anti derivative of one of her ex | |
17:22 | monastery is going to be Ln ex monastery and then | |
17:28 | plus C . Since the constant in front of Ellen | |
17:34 | are different , it might be good to leave it | |
17:37 | in this form . Now you can still combine it | |
17:41 | into its into a single log expression if you want | |
17:44 | to , If you wish to do that . What | |
17:47 | I would do is move the nine here . A | |
17:50 | property of logs allows you to move the coefficient to | |
17:53 | the export position . For instance to L N X | |
17:56 | is equal to L N X square . You can | |
17:59 | move it to to the exploded position of X . | |
18:07 | So first I would rewrite it as 1/8 Ellen and | |
18:12 | this would be X-plus 5 to the knife power but | |
18:17 | still within An absolute value simple and then -1/8 Ellen | |
18:23 | ex monastery plus C . And then we can factor | |
18:27 | out 1/8 at this point and then write it as | |
18:32 | a single lot of expression . So it's gonna be | |
18:34 | one of her eight Ln absolute value X-plus five race | |
18:40 | at a knife power over X minus stream . And | |
18:44 | then plus C . So you can invite it like | |
18:47 | this as a single log if you wish . So | |
18:53 | that's it for this problem . So let's try a | |
18:57 | slightly harder problem . So in this problem we have | |
19:01 | the linear factor X -1 . But we also have | |
19:04 | a repeated Linear Factor X -2 . So how can | |
19:09 | we set up this problem ? Well , what we're | |
19:13 | gonna do is we're going to write three fractions instead | |
19:16 | of two . We're going to have the integral of | |
19:21 | a Over X -1 and then we're going to have | |
19:30 | the integral of B over the other , linear factor | |
19:35 | x minus two . And since it's x minus two | |
19:40 | squared , we're going to have another fraction . This | |
19:43 | one's going to B C Over X -2 Squared . | |
19:50 | So that's what you need to do . If you | |
19:52 | have a repeated linear factors . For instance , let's | |
19:56 | say if we have one over xmas history To the | |
20:01 | 3rd power to break it up using partial fractions , | |
20:06 | this would be a over x minus stream , plus | |
20:10 | a B Over X -3 Squared and then plus C | |
20:15 | over x minus street cube . So that's how we | |
20:18 | would set up the problem . If this was a | |
20:21 | race to the 3rd power , Let's go ahead and | |
20:26 | work on this one . So let's rewrite it without | |
20:33 | the integral symbols . So we're gonna multiply every fraction | |
20:56 | By X -1 times x -2 squared . So when | |
21:03 | multiplying these two , these will completely canceled . Leaving | |
21:08 | behind X on the left side of the equation when | |
21:14 | multiplying these two , X -1 will cancel and we'll | |
21:22 | be left with a Times X -2 Squared . Next | |
21:38 | when multiplying needs to only one Of the two X | |
21:44 | -2 factors will cancel . So we're gonna have to | |
21:47 | be Times X -1 times x -2 . And finally | |
22:01 | the X -2 squared terms will cancel . And we'll | |
22:04 | be left with c . times the factor X -1 | |
22:09 | . Now what we're gonna do is we're gonna plug | |
22:11 | in some numbers . Let's focus on The X -2 | |
22:17 | Factor . So we're going to plug in is we're | |
22:20 | gonna plug in X equals two . This is going | |
22:22 | to be too and then this is going to be | |
22:25 | a 2 -2 is zero and then be two minus | |
22:30 | one is one , 2 -2 is cyril and then | |
22:33 | plus C 2 -1 is one . So we get | |
22:37 | two is equal to see because those they go to | |
22:40 | zero . So let's write that here , C is | |
22:44 | equal to two . Now since we have some X | |
22:51 | -1 factors We're going to plug in x equals one | |
22:57 | . So this is going to be one A And | |
23:00 | then 1 -2 squared plus a . B 1 -1 | |
23:05 | is zero And for C It's 1 -1 which is | |
23:09 | also zero . 1 -2 Squared . That's negative one | |
23:15 | squared Which is a positive one . So basically a | |
23:20 | . Is equal to one . Now to get B | |
23:28 | . We need to plug in some other number that's | |
23:31 | not one or two . So let's pick the next | |
23:34 | best number which is three . This is going to | |
23:37 | be three . A three minus two is 11 squared | |
23:40 | is one And then 3 -1 is 2 3 -2 | |
23:45 | is one And then 3 -1 is two . Now | |
23:50 | we know A . Is one so that becomes one | |
23:54 | and C . Is to so two times two is | |
23:56 | four And 1-plus 4 is five . That is adding | |
24:05 | those two subtracting both sides by five . We're going | |
24:08 | to have three minus five which is negative two . | |
24:11 | And then if we divide both sides by two we'll | |
24:14 | get that be Is equal to -1 . So let's | |
24:22 | replace a with one unless you place be with negative | |
24:34 | one and then see with two The anti derivative of | |
24:50 | one over X -1 is going to be Ln x | |
24:54 | minus one an absolute value . And the next this | |
24:58 | is gonna be negative . Ellen x minus two for | |
25:06 | this one . We could use use substitution . So | |
25:10 | I'm going to rewrite the expression as two times the | |
25:12 | integral of one Over X -2 Squared . So we're | |
25:18 | going to make you equal to X -2 D'you is | |
25:22 | going to equal dx . So this becomes two times | |
25:27 | the integral of one over U squared . Do you | |
25:32 | moving to you variable to the top ? This becomes | |
25:34 | too integral U . To the negative too . Now | |
25:39 | we can integrate using the powerful so we're going to | |
25:42 | add one to the negative two exponents . So it | |
25:44 | becomes U . To the negative one . And then | |
25:47 | we're gonna divided by negative one bringing you back to | |
25:51 | the bottom , this becomes negative to over you And | |
25:54 | then replacing you with X -2 , It becomes -2 | |
25:58 | over X -2 . So this is the answer . | |
26:11 | Now if we want to we can write the to | |
26:15 | log expressions into a single log . So we can | |
26:18 | write as Ellen X -1 over X -2 And then | |
26:24 | -2 Over X -2 Plus C . So we can | |
26:30 | leave the answer like this if we wish . So | |
26:33 | that's it for problem number three go ahead and try | |
26:38 | this problem . Find the anti derivative of X square | |
26:41 | plus nine over x squared minus one times x squared | |
26:45 | plus four . So as always you want to make | |
26:49 | sure that the denominator the fraction is completely factored . | |
26:55 | We can't factor x squared plus four but we can | |
26:58 | factor x squared minus one . Since we have a | |
27:01 | difference of perfect squares . The square root of x | |
27:04 | squared is X . The square root of one is | |
27:07 | one . So we're gonna have X plus one and | |
27:09 | x minus one . So what we have here is | |
27:18 | to linear factors and the quadratic factor . So we | |
27:24 | could set this up as a Over X-plus one and | |
27:33 | then plus B Over X -1 . Now , for | |
27:41 | the quadratic factor x square plus four on top , | |
27:44 | we're going to write C . X plus team instead | |
27:47 | of C or D by itself . So that's how | |
27:56 | we could set up the partial fraction decomposition . Now | |
28:05 | on top , we can write this as the integral | |
28:08 | of A over X plus one dx and then plus | |
28:13 | the integral of B Over X -1 , the X | |
28:18 | . And then plus the integral of C . X | |
28:22 | . Plaza de over X squared plus four . Now | |
28:29 | let's multiply both sides of the equation by this denominator | |
28:33 | here . So I'm just going to write this on | |
28:38 | this side . So we have X plus one , | |
28:41 | X minus one and X squared plus four . So | |
28:46 | these will completely cancel . Leave behind X square plus | |
28:49 | nine on the left side . And then this fraction | |
28:56 | times all of that . The X plus one fact | |
29:00 | the X plus one factors will cancel . Leave behind | |
29:03 | A Times X -1 times X squared plus four . | |
29:09 | Next we're going to play this fraction by that X | |
29:14 | -1 will cancel . So we're going to have be | |
29:19 | Times X-plus one times X squared plus four . It's | |
29:26 | important to be very careful with every step because if | |
29:29 | you make one mistake , this is a long problem | |
29:32 | . The whole problem is is going down the drain | |
29:35 | so it's going to take your time working with these | |
29:39 | problems . So now multiplying this by what we have | |
29:45 | here , X squared plus four will cancel . Leaving | |
29:49 | behind . See explicit E Times X-plus one Times X | |
29:54 | -1 . Now the term X squared plus four will | |
29:59 | always be greater than zero . So there's no X | |
30:03 | value that we can plug in to make that disappear | |
30:06 | . Now we do have some linear factors X -1 | |
30:09 | and X plus one . So we can plug in | |
30:11 | X equals positive one and X equals negative one . | |
30:14 | To turn those linear factors into zero . So let's | |
30:18 | start by plugging X equals positive one first . So | |
30:24 | we're gonna have one square plus one . I mean | |
30:27 | one square plus nine rather and then A times 1 | |
30:33 | -1 is going to be zero . So this Entire | |
30:36 | term becomes zero and then plus B . one Plus | |
30:40 | 1 is two . One square plus four . That's | |
30:43 | going to be five . And here we have an | |
30:47 | X -1 factor . So when we plug in one | |
30:49 | That entire term here is gonna be zero . So | |
30:53 | one plus 9 is 10 , two times 5 is | |
30:56 | 10 . So we have 10 is equal to 10 | |
30:58 | B . The volume both sides by 10 . We | |
31:02 | get that B is equal to one . So let's | |
31:07 | go ahead and replace be with one . So now | |
31:17 | that we use X equals one . Let's try plugging | |
31:21 | in x equals negative one . -1 Squared is still | |
31:35 | one . So we're going to have one plus nine | |
31:37 | which is 10 on the left side and then it's | |
31:41 | gonna be a 1 -1 is negative two negative one | |
31:45 | squared plus four . That's going to be positive one | |
31:48 | plus four which is five . When we plug a | |
31:52 | negative one into X . Plus one , that's going | |
31:54 | to be zero and this will be zero sua So | |
31:58 | we get 10 is equal to negative 10 . A | |
32:02 | dividing both sides by negative 10 . We can see | |
32:05 | that A . Is negative one . Now what's the | |
32:19 | next X . Value that you think we should plug | |
32:21 | in ? I would recommend plug it in X . | |
32:26 | equals zero . We have the valleys for A . | |
32:30 | And B . We have to focus on Cnd if | |
32:33 | we plug in zero C disappears which means we only | |
32:37 | have the leftover which means we could solve for D | |
32:41 | . So on the left we're gonna have zero squared | |
32:43 | plus nine . This is going to equal A . | |
32:46 | We know A . Is negative one And then 0 | |
32:51 | -1 is -1 . Zero square plus four . That's | |
32:55 | four . Be as positive one . zero Plus 1 | |
33:00 | is one . And cyril squared plus four . That's | |
33:03 | going to be four . Again . See explicit E | |
33:05 | . This is going to be see time zero plus | |
33:11 | the D . Zero plus one is 10 minus one | |
33:14 | is negative one . So this is nine negative one | |
33:18 | times negative one times voice four . And then we | |
33:20 | have another four . See time zero plus D . | |
33:24 | Is just A . D . And then we have | |
33:27 | one times negative one . So this is nine is | |
33:30 | equal to eight -D . Subtracting both sides by eight | |
33:34 | . We have 9 -8 which is -1 . And | |
33:38 | that's equal actually that's positive one and that's equal to | |
33:42 | negative D . So D . Is equal to negative | |
33:45 | one . So let's put negative one here for D | |
34:00 | . Now we need to calculate C . To do | |
34:06 | that . Let's pick the next best X . Value | |
34:09 | . And uh Let's go with x equals two . | |
34:19 | Since we know A . B . And C . | |
34:21 | I mean we know a BND . So now we | |
34:23 | can just find the missing constancy . So plugging into | |
34:32 | for X . This is going to be two squared | |
34:34 | plus nine . A . is negative one . Two | |
34:38 | minus one is 12 squared plus four . That's going | |
34:41 | to be eight . B . Is 12 plus one | |
34:45 | . History and two squared plus four is eight . | |
34:47 | Again . See explicit E . We're looking for C | |
34:52 | . We have X which is two . So this | |
34:54 | is going to be C . Times two or to | |
34:56 | see D . is -1 . And then we have | |
35:02 | two plus one which is three 2 -1 which is | |
35:05 | one . Two squared is 44 plus nine is 13 | |
35:10 | . And then we have negative eight plus 24 . | |
35:14 | And then if we distribute three it's a two C | |
35:16 | minus one That becomes six c . Ministry negative eight | |
35:25 | plus 24 That's gonna be 16 . And then we | |
35:31 | have 16 -3 which is 13 . Subtracting 13 from | |
35:38 | both sides 13 -13 0 . And so c . | |
35:42 | is equal to zero . So this becomes zero x | |
35:48 | . Which basically it disappears . So now that we | |
35:53 | have the values of A . B . C . | |
35:54 | And D . We can go ahead and determine the | |
35:59 | integral for this original expression . So the integral of | |
36:06 | negative one over X plus one . That's gonna be | |
36:08 | negative Ln Absolute value expressed one and this is going | |
36:13 | to be plus The Natural Log Absolute Value X -1 | |
36:20 | . Now this part here there's a formula that can | |
36:24 | help us to integrate it . If you wish to | |
36:27 | find the integral of dx over X squared plus a | |
36:33 | squared . This is going to be won over A | |
36:37 | . Are tangent X over A plus C . So | |
36:44 | in this example we can see that A square is | |
36:51 | four . So therefore a . Is too . Now | |
36:54 | we do have a negative one . So we need | |
36:56 | to put a negative here is gonna be negative one | |
36:58 | over A . Or negative 1/2 are tangent X over | |
37:03 | two Plus C . So that's gonna be the integral | |
37:07 | of that expression . Now , if for some reason | |
37:13 | you're not allowed to use that formula and you have | |
37:15 | to show your work , here's what you can do | |
37:22 | . So I'm going to move the negative sign to | |
37:23 | the front . So let's start with this expression we're | |
37:27 | going to use trig substitution . So we're gonna make | |
37:32 | X . Or rather we're gonna make X squared equal | |
37:35 | to four tan squared . So X is going to | |
37:40 | be two tangent data . Dx is going to be | |
37:44 | two times the derivative of tangent which is seeking squared | |
37:48 | theta and then time's D . Data . So this | |
37:53 | is going to be we're going to replace the dX | |
37:56 | with to seek in squared theta . D . Theta | |
38:02 | On the bottom . We have four Tan Square data | |
38:06 | and then plus four . So I replaced the X | |
38:09 | squared dx . Now what we're gonna do now is | |
38:23 | we're gonna factor the four . So we're gonna be | |
38:27 | left with Tangent squared plus one To over four reduces | |
38:35 | to 1/2 . So I'm going to move the one | |
38:37 | half to the front . So we have negative one | |
38:39 | half integral , seek and squared D . Theta one | |
38:44 | plus tan squared is equal to seek and squared . | |
38:49 | So we could cancel seeking squared . So this becomes | |
38:52 | negative 1/2 integral D . Theta which is the integral | |
38:57 | of the fatah is simply fail to . Now we | |
39:00 | need to find out what that is equal to . | |
39:03 | So in this equation I'm going to divide by two | |
39:05 | so we get X over two is equal to tangent | |
39:07 | data . If we take the arc tangent of both | |
39:10 | sides of this equation , we'll get our tangent X | |
39:15 | over two is equal to our tangent of tangent of | |
39:19 | theta . They are tan and tan cancel given us | |
39:22 | data . So data is are tangent X over two | |
39:30 | . And then we could put plus C . So | |
39:32 | that's how you can show your work converting this expression | |
39:38 | into an arc tangent expression . But if you know | |
39:40 | the formula , it will save you time at least | |
39:43 | you know what to do . So what I recommend | |
39:46 | doing if you have to show your work is replace | |
39:48 | the X squared term With four tangent squared . The | |
39:52 | reason why I chose 400 square is because of the | |
39:54 | four here . So you can factor out of four | |
39:57 | . Get tanned square plus one and convert that into | |
40:00 | second squared . So if this was X squared plus | |
40:03 | nine , I would make X squared nine tangent squared | |
40:14 | . So now let's go ahead and finish this problem | |
40:17 | . What we can do is combine this into a | |
40:18 | single log expression , so this is gonna be the | |
40:21 | natural log , we're going to put the positive one | |
40:23 | on top , so it's X minus one over X | |
40:27 | plus one and then minus one half arc tangent X | |
40:34 | over two Plus C . So that's the answer for | |
40:39 | this problem . |
DESCRIPTION:
This calculus video tutorial provides a basic introduction into integrating rational functions using the partial fraction decomposition method. Partial fraction decomposition is the process of breaking a single complex fraction into multiple simpler fractions. The integrals of many rational functions lead to a natural log function with absolute value expressions. This video explains what to do when you have repeated linear factors and quadratic factors. This tutorial contains many examples and practice problems on integration by partial fractions.
OVERVIEW:
Integration By Partial Fractions is a free educational video by The Organic Chemistry Tutor.
This page not only allows students and teachers view Integration By Partial Fractions videos but also find engaging Sample Questions, Apps, Pins, Worksheets, Books related to the following topics.