X+y-x³-y³=(x+y)-(x³+y³)=(x+y)-(x+y)(x²-xy+y²)=(x+y)(1-x²+xy-y²)
X 3 – 3 x 2 y – 4 xy + 12 y 2 = ( x 3 – 3 x 2 y ) – (4 xy – 12 y 2 )