已知1/a+1/b=2,则3a-2ab+3b/-4a+5ab-4b=
问题描述：
已知1/a+1/b=2,则3a-2ab+3b/-4a+5ab-4b=
答
-4/3
答
1/a+1/b=2
b/ab+a/ab=2
(a+b)/ab=2
a+b=2ab
(3a-2ab+3b)/(-4a+5ab-4b)
=(6ab-2ab)/(-8ab+5ab)
=-4/3