(1)计算:9-(12)-1+(2-2)0-2cos60°;(2)先化简:(1x+1-1)÷xx2-1,再选择一个恰当的x值代入求值.-数学

题目简介

(1)计算:9-(12)-1+(2-2)0-2cos60°;(2)先化简:(1x+1-1)÷xx2-1,再选择一个恰当的x值代入求值.-数学

题目详情

(1)计算:
9
-(
1
2
)-1+(2-
2
)0
-2cos60°;
(2)先化简:(
1
x+1
-1
÷
x
x2-1
,再选择一个恰当的x值代入求值.
题型:解答题难度:中档来源:贵港

答案

(1)
9
-(class="stub"1
2
)-1+(2-
2
)0-2cos60°
=3-2+1-2×class="stub"1
2

=3-2+1-1
=1;

(2)(class="stub"1
x+1
-1)÷class="stub"x
x2-1

=class="stub"1-x-1
x+1
÷class="stub"x
(x+1)(x-1)

=class="stub"-x
x+1
(x+1)(x-1)
x

=1-x,
要使分式有意义,则(x+1)(x-1)≠0,x≠0,
解得x≠±1,x≠0,
所以,x=2时,原式=1-2=-1.

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