(x/2-y)的平方-1/4(x+y)(x-y)要过程
问题描述：
(x/2-y)的平方-1/4(x+y)(x-y)要过程
答
(x/2-y)的平方-1/4(x+y)(x-y)
=1/4[(x-2y)的平方-(x+y)(x-y)]
=1/4(x^2-4xy+4y^2-x^2+y^2)
=1/4(5y^2-4xy)
=5y^2/4-xy