Question

已知a分之1-b分之1=4则2a-2b+7ab分之a-2ab-b=?

Answer 1

2a-2b+7ab分之a-2ab-b
=（a-2ab-b）/(2a-2b+7ab) 分子分母同时除以ab ab都不为0
=(1/b - 2 - 1/a)/(2/b-2/a+7)
=(-2- (1/a - 1/b))/(7-2(1/a - 1/b))
=(-2-4)/(7-2*4)
=-6/(-1)
=6

Answer 2

1/a+1/b=4
a+b=4ab
(a+b-3ab)/(2a+2b-7ab)
=(4ab-3ab)/(2*4ab-7ab)
=ab/(ab)
=12a-2b+7ab分之a-2ab-b
=（a-2ab-b）/(2a-2b+7ab) 分子分母同时除以ab ab都不为0
=(1/b - 2 - 1/a)/(2/b-2/a+7)
=(-2- (1/a - 1/b))/(7-2(1/a - 1/b))
=(-2-4)/(7-2*4)
=-6/(-1)
=6我也不知道到底那个对。：）！