How do you factor 128x^3 - 1024128x31024?

1 Answer
Feb 6, 2017

128(x-2)(x^2+2x+4)128(x2)(x2+2x+4)

Explanation:

The 2 terms have a color(blue)"common factor"common factor of 128, which can be taken out.

rArr128(x^3-8)to(A)128(x38)(A)

x^3-8x38 is a color(blue)"difference of cubes"difference of cubes which, in general, is factorised as shown.

color(red)(bar(ul(|color(white)(2/2)color(black)(a^3-b^3=(a-b)(a^2+ab+b^2))color(white)(2/2)|)))

using a = x and b = 2, then

rArrx^3-8=(x-2)(x^2+2x+2^2)=(x-2)(x^2+2x+4)

Returning to (A) the complete factorisation is.

128x^3-1024=128(x-2)(x^2+2x+4)