已知1/a−1/b=5,求2a+3ab−2ba−2ab−b的值.

问题描述:

已知

1
a
1
b
=5,求
2a+3ab−2b
a−2ab−b
的值.

1
a
-
1
b
=
b−a
ab
=5,
∴b-a=5ab,即a-b=-5ab,
2a+3ab−2b
a−2ab−b

=
2(a−b)+3ab
(a−b)−2ab

=
−10ab+3ab
−5ab−2ab

=
−7ab
−7ab

=1.