先化简再求值4x^2-8xy+4y^2/2x^2-2y^2,其中x=2,y=3
问题描述：
先化简再求值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)
=[4(x^2-2xy+y^2)]/[2(x^2-y^2)]
=[4(x-y)^2)]/[2(x-y)(x+y)]
=2(x-y)/(x+y)
=2*(2-3)/(2+3)
=-2/5