Question

1) (a+b)^3
2) (x-3y)^3

Answer 1

$displaystyle tt 1) : (a+b)^3=bold{a^3+3a^2b+3ab^2+b^3}\displaystyle tt 2) : (x-3y)^3=x^3-3x^2cdot3y+3xcdot(3y)^2-(3y)^3=x^3-9x^2y+3xcdot9y^2-27y^3=bold{x^3-9x^2y+27xy^2-27y^3}$