Expert: Richard J. Raridon - 3/16/2008

Question
I have the follwing equation (2x+3)^3 - 64. The book gives the answer (2x-1)(4x^2 + 20x +37). I cannot figure out how they got this answer. I also have a similar problem for which the answe is not given in the book:(4x+2)^3 - 125. Here I am confused, since there is a GCF -how I go about it.
Your help would be most appreciated.

Answer
That's an expression, not an equation, since you don't have an equals sign.                                                        If you multiply out (2x+3)^3 -64 you get 8x^3 +36x +54x -37
which factors to (2x-1)(4x^2+20x+37)
(4x+2)^3 -125 = 64x^3 +96x^2 +48x -117 = (4x-3)(16x^2+36x+39)