化简求值4x^2-8xy+4y^2/2x^2-2y^2其中x=2.y=3
问题描述：
化简求值4x^2-8xy+4y^2/2x^2-2y^2其中x=2.y=3
答
4x^2-8xy+4y^2/2x^2-2y^2
=（2x-2y)^2/[2(x^2-y^2)]
=4(x-y)^2/[2(x-y)(x+y)]
=2(x-y)/(x+y)
=-2/5