题目内容
解答下列各题:(1)计算:-22×
8 |
2 |
(2)先化简再求值:(x5+3x3)÷x3-(x+1)2,其中x=-
1 |
2 |
(3)化简:
2 |
a+1 |
a-2 |
a2-1 |
a2-2a |
a2-2a+1 |
分析:本题的关键是化简,然后把给定的值代入求值.化简第三题关键是通分与约分.
解答:解:(1)原式=-8
+2
+6
=0;
(2)原式=(x2+3)-(x+1)2=x2+3-x2-1-2x=-2x+2,
将x=-
代入得:原式=-2x+2=3;
(3)原式=
-
×
=
-
=
-
=
=
.
2 |
2 |
2 |
(2)原式=(x2+3)-(x+1)2=x2+3-x2-1-2x=-2x+2,
将x=-
1 |
2 |
(3)原式=
2 |
a+1 |
a-2 |
(a-1)(a+1) |
(a-1)2 |
a(a-2) |
2 |
a+1 |
a-1 |
a(a+1) |
2a |
a(a+1) |
a-1 |
a(a+1) |
2a-(a-1) |
a(a+1) |
1 |
a |
点评:利用公式可以适当简化一些式子的计算.
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