Question

先化简，再求值[(x+y)(x-y)-(x-y)²+2y(x-y)]÷4y,其中x=1,y=-3

Answer 1

就是提公因式然后化解。祝学习进步！

Answer 2

[(x+y)(x-y)-(x-y)²+2y(x-y)]÷4y
=(x－y)[(x＋y)－(x－y)＋2y]÷4y
=4y(x－y)÷4y
=x－y
再将x=1,y=-3代入有
原式=x－y
=1－(﹣3)
=4