Question

How do you multiply `(x + 5y)^3`?

Answer 1

`x^3+15x^2y+75xy^2+125y^3`

Explanation:

Given: `(x+5y)^3`.

Use the fact that `(a+b)^3=a^3+3a^2b+3ab^2+b^3`.

Letting `a=x,b=5y`, we get:

`=x^3+3*x^2*5y+3*x*(5y)^2+(5y)^3`

`=x^3+15x^2y+3x*25y^2+125y^3`

`=x^3+15x^2y+75xy^2+125y^3`