问题
解答题
先化简，再求值：(
|
答案
(
-1 x-y
)÷1 x+y
=2y x2+2xy+y2
•(x+y)-(x-y) (x-y)(x+y) (x+y)2 2y
=
•2y (x-y)(x+y)
=(x+y)2 2y
，x+y x-y
把x=
+3
，y=2
-3
代入上式，得2
原式=
=(
+3
)+(2
-3
)2 (
+3
)-(2
-3
)2
=2 3 2 2
．6 2