问题
解答题
先化简,再求值.(
|
答案
原式=[
+(
+x
)2y
+x y
]•
+x y (
-x
)(y
+x
)y x x-y+1
=[
+(x-y)(
+x
)y x-y
]•
+x y x-y x x-y+1
=
•(x-y+1)(
+x
)y x-y x x-y+1
=
,x+ xy x-y
当x=2-
,y=2+3
时,原式=3
=2-
+3 (2-
)(2+3
)3 2-
-2-3 3
=2- 3 -2 3
.3-2 3 6