(x+2y)to the third power equals what?

1 Answer
Mar 25, 2018

(x+2y)^3 = x^3 + 6 x^2 y + 12 x y^2 + 8 y^3

Explanation:

First write it out as (x+2y)(x+2y)(x+2y)
Expand two brackets first, giving: (x^2+2xy+2xy+4y^2)(x+2y) => (x^2+4xy+4y^2)(x+2y)

Then expand again giving:
x^3 + 2x^2y+4x^2y+8xy^2+4xy^2+8y^3

Which simplfies to our answer:
x^3 + 6 x^2 y + 12 x y^2 + 8 y^3