Question

x³+y³-12xy+64,when x+y=-4

Answer 1

x+y = -4
cubing both sides
(x+y)^3 = -64
x^3 +y^3 +3xy(x+y) = -64
x^3 +y^3 +3xy(-4) = -64 {x+y = -4}
x^3 +y^3 -12xy = -64
x^3 +y^3 -12xy +64 = 0