Question

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

Answer 1

`27x^3+81x^2y+81xy^2+27y^3`.

Explanation:

We know that `: (a+b)^3=a^3+b^3+3ab(a+b)`

Now, `(3x+3y)^3={3(x+y)}^3=3^3*(x+y)^3`

`=27{x^3+y^3+3xy(x+y)}`

`=27(x^3+y^3+3x^2y+3xy^2)`

`=27x^3+81x^2y+81xy^2+27y^3`.