http://www.ixl.com/math/algebra-1/solve-a-quadratic-equation-using-square-roots
Source: www.ixl.com
http://www.ixl.com/math/algebra-1/simplify-radical-expressions-by-rationalizing-the-denominator
http://coolmath.com/algebra/09-solving-quadratics/04-solving-quadratic-equations-square-root-01.htm
Source: www.coolmath.com