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．
答
{(x-1)^2-y^2}/(x+y-1)=(x-1-y)(x-1+y)/(x+y-1)=x-y-1=11
答
(x2-2x+1-y2)/(x+y-1)
=(x+y-1)(x-y-1)/(x+y-1)
=x-y-1
当x-y=12时，其值为11
答
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
答
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