x3y-xy3+x2+y2+1

题目

x3y-xy3+x2+y2+1

答案

x3y-xy3+x2+y2+1
=xy(x2-y2)+(x2+y2)+1
=xy(x+y)(x-y)+(x2+y2)+1
利用交叉法,得：
=[x(x-y)+1][y(x+y)]+1)]
=(x2-xy+1)(y2+xy+1)