问题
解答题
先化简,再求值:
|
答案
-1 2x
(x2-y2+1 x+y
)x+y 2x
=
-1 2x
[(x+y)(x-y)+1 x+y
]x+y 2x
=
-(x-y)-1 2x 1 2x
=y-x,
∴当x=1,y=3时,原式=3-1=2.
先化简,再求值:
|
-1 2x
(x2-y2+1 x+y
)x+y 2x
=
-1 2x
[(x+y)(x-y)+1 x+y
]x+y 2x
=
-(x-y)-1 2x 1 2x
=y-x,
∴当x=1,y=3时,原式=3-1=2.