How do you factor 125x^3+8g^3125x3+8g3?

1 Answer
Feb 13, 2017

125x^3+8g^3=(5x+2g)(25x^2-10xg+4g^2)125x3+8g3=(5x+2g)(25x210xg+4g2)

Explanation:

As 125x^3+8g^3=(5x)^3+(2g)^3125x3+8g3=(5x)3+(2g)3, it can be factorized using identity x^3+y^3=(x+y)(x^2-xy+y^2)x3+y3=(x+y)(x2xy+y2)

and 125x^3+8g^3=(5x)^3+(2g)^3125x3+8g3=(5x)3+(2g)3

= (5x+2g)((5x)^2-(5x)xx(2g)+(2g)^2)(5x+2g)((5x)2(5x)×(2g)+(2g)2)

= (5x+2g)(25x^2-10xg+4g^2)(5x+2g)(25x210xg+4g2)

For a proof of the identity see below.

x^3+y^3x3+y3

= x^3+x^2y-x^2y-xy^2+xy^2+y^3x3+x2yx2yxy2+xy2+y3

= x^2(x+y)-xy(x+y)+y^2(x+y)x2(x+y)xy(x+y)+y2(x+y)

= (x+y)(x^2-xy+y^2)(x+y)(x2xy+y2)