问题 填空题
计算:
b+1
a
a+1
b
-
b-1
a
a-1
b
=______.
答案

b+1
a
a+1
b
-
b-1
a
a-1
b
=
(b+1)(a+1)
ab
-
(b-1)(a-1)
ab
=
ab+a+b+1-(ab-b-a+1)
ab
=
2(a+b)
ab

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