已知x=y+2,求[(x+y)(x-y)-(x-y)的2次方+2y(x-y)]÷4y的值

题目

已知x=y+2,求[(x+y)(x-y)-(x-y)的2次方+2y(x-y)]÷4y的值

答案

x=y+2
所以x-y=2
原式=(x²-y²-x²+2xy-y²+2xy-2y²)÷4y
=(-4y²+4xy)÷4y
=x-y
=2