How do you factor (3x-4)^3 + 27(3x4)3+27?

1 Answer
Apr 10, 2015

This is a sum of two cubes. Memorize the rule:

a^3+b^3=(a+b)(a^2-ab+b^2)a3+b3=(a+b)(a2ab+b2)

In this example, a=color(red)((3x-4))a=(3x4) and b=3b=3, so

color(red)((3x-4)^3)+3^3=(color(red)((3x-4))+3)(color(red)((3x-4)^2)-color(red)((3x-4))3+3^2)(3x4)3+33=((3x4)+3)((3x4)2(3x4)3+32)

This answer can be simplified to get:

(3x-1)(x^2-24x+16-9x+12+9)=(3x-1)(x^2-33x+37)(3x1)(x224x+169x+12+9)=(3x1)(x233x+37)