题目内容
计算,化简,求值
(1)(-1)-3+(72+99-2)•[(
)-2-1
]
(2)(x2-1)(
-
),并从-1,0,1,2四个数中任选一个作为x的值,代入求值.
(1)(-1)-3+(72+99-2)•[(
| ||
2 |
1 |
3 |
(2)(x2-1)(
x-1 |
x2+x |
1-x |
x3-x |
(1)原式=-1+(49+
)•(
-
),
=-1;
(2)原式=(x2-1)[
+
],
=(x+1)(x-1)×
,
=x-1,
∵x2-1≠0,x≠0,
∴x≠±1,x≠0,
∴当x=2时,原式=2-1=1.
1 |
992 |
4 |
3 |
4 |
3 |
=-1;
(2)原式=(x2-1)[
x-1 |
x(x+1) |
1 |
x(x+1) |
=(x+1)(x-1)×
x |
x(x+1) |
=x-1,
∵x2-1≠0,x≠0,
∴x≠±1,x≠0,
∴当x=2时,原式=2-1=1.
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