If x + y + 3 = 0, then find the value of $x^3 + y^3 -9xy +9$.

-18 -36 18 36

-18

If x + y + 3 = 0 then , x + y = -3 cubing on both side=  ( x + y)3 = (-3)3 x3 + y3 + 3xy(x + y) = -27 x3 + y3 + 3xy(-3) = -27 x3 + y3 + -9xy = -27 then, $x^3 + y^3 -9xy +9$ = $-27 +9$ = -18