问题
解答题
先化简,再求值: (1)(
(2)
|
答案
(1)原式=
•x+y-x+y (x+y)(x-y)
=(x-y)2 2y
,x-y x+y
当x=1+
,y=1-2
时,原式=2
=2 2 2
;2
(2)原式=2
+3x
-2x
=3x
,x
当x=9时,原式=9.
先化简,再求值: (1)(
(2)
|
(1)原式=
•x+y-x+y (x+y)(x-y)
=(x-y)2 2y
,x-y x+y
当x=1+
,y=1-2
时,原式=2
=2 2 2
;2
(2)原式=2
+3x
-2x
=3x
,x
当x=9时,原式=9.