问题 解答题
化简下列各式:
(1)
a2-4
a2-9
a-3
2a+4

(2)
4-x
x-2
÷(x+2-
12
x-2
)
答案

(1)原式=

(a+2)(a-2)
(a+3)(a-3)
a-3
2(a+2)
=
a-2
2(a+3)

(2)原式=

4-x
x-2
÷
(x+2)(x-2)-12
x-2
=
4-x
x-2
÷
x2-4-12
x-2
=
4-x
x-2
÷
(x+4)(x-4)
x-2
=
4-x
x-2
x-2
(x+4)(x-4)
=-
1
x+4

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