题目内容
(1)计算:-22+(
)0+2sin30°
(2)先化简,再求值
+
÷x,其中x=
.
1 | ||
|
(2)先化简,再求值
x2-1 |
x2-2x+1 |
x2-2x |
x-2 |
1 |
2 |
分析:(1)求出22=4,(
)0=1,sin30°=
,再代入求出即可;
(2)先把分式的分子和分母分别分解因式,再约分,约分后进行加法运算,最后代入求出即可.
1 | ||
|
1 |
2 |
(2)先把分式的分子和分母分别分解因式,再约分,约分后进行加法运算,最后代入求出即可.
解答:(1)解:原式=-4+1+2×
=-4+1+1
=-2;
(2)解:∵x=
,
∴原式=
+
×
,
=
+1,
=
+
,
=
,
=
,
=-2.
1 |
2 |
=-4+1+1
=-2;
(2)解:∵x=
1 |
2 |
∴原式=
(x+1)(x-1) |
(x-1)2 |
x(x-2) |
x-2 |
1 |
x |
=
x+1 |
x-1 |
=
x+1 |
x-1 |
x-1 |
x-1 |
=
2x |
x-1 |
=
2×
| ||
|
=-2.
点评:本题考查的知识点是零指数幂、特殊角的三角函数值、分式的加减法等,能熟练地运用法则进行计算和化简是解此题的关键.
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