约分4x^2-y^2/-2x-y
问题描述：
约分4x^2-y^2/-2x-y
答
平方差公式
4x^2-y^2/-2x-y
=(2x+y)(2x-y)/[-(2x+y)]
=y-2x
答
4x^2-y^2/-2x-y
=(2x+y)(2x-y)/[-(2x+y)]
=y-2x