ab/a+b=3 a-2ab+b/2a-3ab+2b?

问题描述:

ab/a+b=3 a-2ab+b/2a-3ab+2b?

ab/a+b=3
∴ab=3a+3b
(a-2ab+b)/(2a-3ab+2b)
=[a-2(3a+3b)+b]/[2a-3(3a+3b)+2b]
=-5(a+b)/[-7(a+b)]
=5/7