(1)计算:(2-1)-2+8-6sin45°+(-1)2009;(2)先化简再求值:(a-a2-b2+1a)÷b-1a×1a+b,其中a=-12,b=-2.-数学

题目简介

(1)计算:(2-1)-2+8-6sin45°+(-1)2009;(2)先化简再求值:(a-a2-b2+1a)÷b-1a×1a+b,其中a=-12,b=-2.-数学

题目详情

(1)计算:(
2
-1)-2+
8
-6sin45°+(-1)2009
(2)先化简再求值:(a-
a2-b2+1
a
b-1
a
×
1
a+b
,其中a=-
1
2
,b=-2.
题型:解答题难度:中档来源:呼和浩特

答案

(1)(
2
-1)-2+
8
-6sin45°+(-1)2009
=class="stub"1
(
2
-1)2
+2
2
-3
2
-1
=3+2
2
+2
2
-3
2
-1
=2+
2


(2)(a-
a2-b2+1
a
)÷class="stub"b-1
a
×class="stub"1
a+b

=
a2-a2+b2-1
a
×class="stub"a
b-1
×class="stub"1
a+b

=
(b+1)(b-1)
a
×class="stub"a
b-1
×class="stub"1
a+b

=class="stub"b+1
a+b

当a=-class="stub"1
2
,b=-2时,
原式=class="stub"-1
-class="stub"5
2
=class="stub"2
5

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