(1)化简:45+1220-515(2)先化简,再求值:aa+3-3a-9a2-9,其中a=1.-数学

题目简介

(1)化简:45+1220-515(2)先化简,再求值:aa+3-3a-9a2-9,其中a=1.-数学

题目详情

(1)化简:
45
+
1
2
20
-5
1
5

(2)先化简,再求值:
a
a+3
-
3a-9
a2-9
,其中a=1.
题型:解答题难度:中档来源:不详

答案

(1)原式=
9×5
+class="stub"1
2
4×5
-5
class="stub"5
5×5

=3
5
+class="stub"1
2
×2
5
-5×class="stub"1
5
5

=3
5
+
5
-
5

=3
5


(2)原式=class="stub"a
a+3
-
3(a-3)
(a+3)(a-3)

=class="stub"a
a+3
-class="stub"3
a+3

=class="stub"a-3
a+3

当a=1时,原式=-class="stub"1
2

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