化简与计算(1)计算:a2a-2+42-a;12m2-9-2m-3.(2)先化简再求值(3xx-2-xx+2)÷2xx2-4,其x=3-4;a2-4a2+6a+9÷a-22a+6,其中a=-5.-数学

题目简介

化简与计算(1)计算:a2a-2+42-a;12m2-9-2m-3.(2)先化简再求值(3xx-2-xx+2)÷2xx2-4,其x=3-4;a2-4a2+6a+9÷a-22a+6,其中a=-5.-数学

题目详情

化简与计算
(1)计算:
a2
a-2
+
4
2-a

12
m2-9
-
2
m-3

(2)先化简再求值
(
3x
x-2
-
x
x+2
2x
x2-4
,其x=
3
-4

a2-4
a2+6a+9
÷
a-2
2a+6
,其中a=-5.
题型:解答题难度:中档来源:不详

答案

(1)原式=
a2
a-2
-class="stub"4
a-2

=
a2-4
a-2

=a+2;
原式=class="stub"12
(m+3)(m-3)
-
2(m+3)
(m+3)(m-3)

=class="stub"12-2m-6
(m+3)(m-3)

=class="stub"6-2m
(m+3)(m-3)

=-class="stub"2
(m+3)


(2)原式=
3x(x+2)-x(x-2)
(x-2)(x+2)
÷class="stub"2x
(x+2)(x-2)

=
2x(x+4)
(x+2)(x-2)
×
(x+2)(x-2)
2x

=x+4,
当x=
3
-4时,原式=
3
-4+4=
3

原式=
(a+2)(a-2)
(a+3)2
×
2(a+3)
a-2

=
2(a+2)
a+3

当a=-5时,原式=
2(-5+2)
-5+3
=3.

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