✨ Best Answer ✨
x(x+1)(x+2)-y(y+1)(y+2)+xy(x-y)
=x³+3x²+2x-y³-3y²-2y+xy(x-y)
=x³-y³+3(x²-y²)+2(x-y)+xy(x-y)
=(x-y)(x²+xy+y²)+3(x+y)(x-y)
+2(x-y)+xy(x-y)
=(x-y){(x²+xy+y²)+3(x+y)+2+xy}
=(x-y){x²+2xy+y²+3(x+y)+2}
=(x-y){(x+y)²+3(x+y)+2}
=(x-y)(x+y+1)(x+y+2)

ありがとうございます!