问题
解答题
先化简,再求值:
|
答案
-x x-1
-1=3 (x-1)(x+2) x(x+2)-3-(x-1)(x+2) (x-1)(x+2)
=x2+2x-3-x2-2x+x+2 (x-1)(x+2)
=x-1 (x-1)(x+2)
=
;1 x+2
∴当x=-
时,原式的值为2 3
=1 -
+22 3
.3 4
先化简,再求值:
|
-x x-1
-1=3 (x-1)(x+2) x(x+2)-3-(x-1)(x+2) (x-1)(x+2)
=x2+2x-3-x2-2x+x+2 (x-1)(x+2)
=x-1 (x-1)(x+2)
=
;1 x+2
∴当x=-
时,原式的值为2 3
=1 -
+22 3
.3 4