Question

How do you expand `(x-9y)^2`?

Answer 1

`x^2-18xy+81y^2`.

Explanation:

We use the Formula `: (a-b)^2=a^2-2ab+b^2`.

Hence, `(x-9y)^2=x^2-2*x*9y+(9y)^2`

`=x^2-18xy+81y^2`.