Question

If x+y=4 find x^3+y^3+12xy-6y

Answer 1

x^3+y^3+12xy-6y = (x+y)( x^2 -xy +y^2)+12xy + 6y = 4{(x+y)^2-3xy} + 12xy -6 y
{4(4)^2-12xy } +12xy -6y
64-6y