Simplify fully (y+3)^2

Firstly expand the brackets to make (y+3)(y+3)Next I find it easy to remember that you don't times anything together that's in the same bracket when expanding. So - y x y = y^2y x 3 = 3y3 x y = 3y3 x 3 = 9So in total this is y^2 + 6y + 9