x³+y³+2xy(x+y) = (x+y)(x²-xy+y²) + 2xy(x+y)x³+y³+2xy(x+y) = (x+y)(x²-xy+y²+2xy)x³+y³+2xy(x+y) = (x+y)(x²+xy+y²)
x³+y³+2xy(x+y) = (x+y)(x²-xy+y²) + 2xy(x+y)
x³+y³+2xy(x+y) = (x+y)(x²-xy+y²+2xy)
x³+y³+2xy(x+y) = (x+y)(x²+xy+y²)