Question

How do you multiply and simplify the following expression completely `(x-2y)^3`?

Answer 1

The rule is:

`(a-b)^3=a^3-3a^2b+3ab^2-b^3`.

So:

`(x-2y)^3=x^3-3(x)^2(2y)+3x(2y)^2-(2y)^3=`

`=x^3-6x^2y+12xy^2-8y^3`.