问题 解答题
化简
(1)(1-
y
y+x
x
y2-x2

(2)(
a2
a-3
+
9
3-a
÷
a+3
a
     
(3)(1+
3
a-2
a+1
a2-4
答案

(1)原式=(

y+x
y+x
-
y
y+x
)•
(y+x)(y-x)
x
=
x
y+x
(y+x)(y-x)
x
=y-x;

(2)原式=

a2-9
a-3
a
a+3
=
(a+3)(a-3)
a-3
a
a+3
=a;

(3)原式=

a-2+3
a-2
(a+2)(a-2)
a+1
=
a+1
a-2
(a+2)(a-2)
a+1
=a+2.

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