已知1/a−1/b=5,求2a+3ab−2ba−2ab−b的值.
问题描述:
已知
−1 a
=5,求1 b
的值. 2a+3ab−2b a−2ab−b
答
∵
-1 a
=1 b
=5,b−a ab
∴b-a=5ab,即a-b=-5ab,
则
2a+3ab−2b a−2ab−b
=
2(a−b)+3ab (a−b)−2ab
=
−10ab+3ab −5ab−2ab
=
−7ab −7ab
=1.