先化简(x2-2x+1-y2)/(x+y-1),并求当x-y=12时,该式的值.

问题描述:

先化简(x2-2x+1-y2)/(x+y-1),并求当x-y=12时,该式的值.

原式=((x-1)^2-y^2)/(x+y-1)
=((x-1+y)(x-1-y))/(x+y-1)
=x-y-1
当x-y=12时
原式=11