Solving Logarithmic Equations | MathHelp.com - Free Educational videos for Students in K-12 | Lumos Learning

Solving Logarithmic Equations | MathHelp.com - Free Educational videos for Students in k-12


Solving Logarithmic Equations | MathHelp.com - By MathHelp.com



Transcript
00:0-1 here were asked to solve for X . In the
00:02 equation log base X of 1 44 equals two .
00:08 Notice that we have a log arrhythmic equation . So
00:11 let's first convert the equation to exponential form . Remember
00:16 that the base of the log represents the base of
00:19 the power , the right side of the equation represents
00:23 the exponent and the number inside the log represents the
00:27 result . So we have X Squared equals 1 44
00:34 . Now to solve for X since x is squared
00:39 , we simply take the square root of both sides
00:41 of the equation . To get x equals plus or
00:45 -12 . Remember to always use plus or minus when
00:50 taking the square root of both sides of an equation
00:53 . However , notice that X represents the base of
00:57 the law algorithm in the original problem and the base
01:01 of al algorithm cannot be negative , Therefore X cannot
01:06 be equal to -12 . So our final answer is
01:11 x equals 12 .
Summarizer

DESCRIPTION:

Here we’re asked to evaluate each of the following logarithms. In part a, we have log base 7 of 49. To evaluate this logarithm, we set it equal to x. In other words, log base 7 of 49 = what? Notice that we now have an equation written in logarithmic form, so let’s see if we can solve the equation by converting it to exponential form. Remember that the base of the log represents the base of the power, the right side of the equation represents the exponent, and the number inside the log represents the result, so we have 7…to the x…= 49. Next, we solve for x. Notice that 7 and 49 have a like base of 7, so we rewrite 49 as 7 squared, and we have 7 to the x = 7 squared, so x must equal 2. In part b, we have log base 3 of 1/27. Again, to evaluate this logarithm, we set it equal to x, and convert the logarithmic equation to exponential form. Remember that the base of the log represents the base of the power, the right side of the equation represents the exponent, and the number inside the log represents the result, so we have 3…to the x…= 1/27. Next, we solve for x. Notice that 3 and 1/27 have a like base of 3, so we rewrite 1/27 as 1 over 3 cubed, and we have 3 to the x = 1 over 3 cubed. Next, 1 over 3 cubed is the same thing as 3 to the negative 3, so we have 3 to the x = 3 to the negative 3, which means that x must equal -3. Therefore, log base 3 of 1/27 = -3. So remember the following rule. To evaluate a logarithm, set it equal to x, convert to exponential form, and solve the equation using like bases.

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