Question

If x+y = 4 then the value of x^3+y^3-64 +12xy is

Answer 1

x^3+y^3+12xy-64
(x+y)(x^2+y^2-xy)+12xy-64
4(x^2+y^2-xy)+12xy-64
4x^2+4y^2-4xy+12xy-64
4x^2+4y^2+8xy-64
4(x+y)^2-64
64-64
0