已知1/a-1/b=1,求分式2a+3ab-2b/a-2ab-b
问题描述：
已知1/a-1/b=1,求分式2a+3ab-2b/a-2ab-b
答
1/a-1/b=1
b-a=ab
2a+3ab-2b/a-2ab-b
=[2(a-b)+3ab]/[(a-b)-2ab]
=(-2ab+3ab)/(-ab-2ab)
=ab/(-3ab)
=-1/3