1+2xy-x²-y²=?
问题描述:
1+2xy-x²-y²=?
还有一道:ax²+ay²-2axy-a^3
答
1+2xy-x²-y²
=1-(x²+y²-2xy)
=1-(x-y)²
=(1+x-y)(1-x+y)