先化简,再求值:(a+1a2-a-aa2-2a+1)÷1a,其中a=3+1.-数学

题目简介

先化简,再求值:(a+1a2-a-aa2-2a+1)÷1a,其中a=3+1.-数学

题目详情

先化简,再求值:(
a+1
a2-a
-
a
a2-2a+1
1
a
,其中a=
3
+1
题型:解答题难度:中档来源:不详

答案

原式=[class="stub"a+1
a(a-1)
-class="stub"a
(a-1)2
]×a
l分
=class="stub"a+1
a(a-1)
×a-
a2
(a-1)2
=
(a+1)(a-1)
(a-1)2
-
a2
(a-1)2
(3分)
=
a2-1-a2
(a-1)2
=-class="stub"1
(a-1)2
(4分)
a=
3
+1
时,原式=-class="stub"1
(
3
+1-1)
2
=-class="stub"1
3
(6分)

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