x²-y²+x+y
=（x+y）（x-y）+x+y
=(x+y)(x-y+1)
x³-xy²+x+y
=x(x²-y²)+x+y
=x(x+y)(x-y)+x+y
=(x+y)(x²-xy+1)
如果本题有什么不明白可以追问,