Common Core State Standard: 8.EE.2 

Grade  8 
Subject  MATH 
Domain  Expressions & Equations 
Theme  Work with radicals and integer exponents 
Standard  Use square root and cube root symbols to represent solutions to equations of the form x^2 = p and x^3 = p, where p is a positive rational number. Evaluate square roots of small perfect squares and cube roots of small perfect cubes. Know that ?2 is irrational. 
Reference URL  http://www.corestandards.org/Math/Content/8/EE 