Question

已知1/a-1/b=3，求分式2a+3ab-2b/a-ab-b的值

Answer 1

1/a-1/b=3
(b-a)/ab=3
b-a=3ab
2a+3ab-2b/a-ab-b
=(2a+b-a-2b)[a-b-(b-a)/3]
=(a-b)/[4(a-b)/3]
=3/4

或者
2a+3ab-2b/a-ab-b
=[2(-3ab)+3ab]/(-3ab-ab)
=3/4

Answer 2

/a-1/b=3,
(b-a)/ab=3
b-a=3ab
a-b=-3ab

(2a+3ab-2b)/(a-ab-b)
=[2(a-b)+3ab]/[(a-b)-ab]
=(-6ab+3ab)/(-3ab-ab)
=-3ab/(-4ab)
=3/4

Answer 3

我不是他舅|二十级
1/a-1/b=3,
(b-a)/ab=3
b-a=3ab
a-b=-3ab

(2a+3ab-2b)/(a-ab-b)
=[2(a-b)+3ab]/[(a-b)-ab]
=(-6ab+3ab)/(-3ab-ab)
=-3ab/(-4ab)
=3/4赞同90|评论(6) 按默认排序|按时间排序
其他回答 共8条 检举|2011-02-24 21:50欧阳上智|六级/a-1/b=3,
(b-a)/ab=3
b-a=3ab
a-b=-3ab

(2a+3ab-2b)/(a-ab-b)
=[2(a-b)+3ab]/[(a-b)-ab]
=(-6ab+3ab)/(-3ab-ab)
=-3ab/(-4ab)
=3/4[提问者认可]|赞同40|评论 检举|2011-03-08 18:53wqqts|十七级1/a-1/b=3
(2a+3ab-2b)/(a-ab-b)
分子分母同除以ab
(2/b+3-2/a)/(1/b-1-1/a)
={-2(1/a-1/b)+3} / {-(1/a-1/b)-1}
={-2*3+3}/{-3-1}
=-3/(-4)
=3/4[提问者认可]|赞同15|评论 检举|2012-02-11 14:52370116|二十级1/a-1/b=3
(b-a)/ab=3
b-a=3ab
2a+3ab-2b/a-ab-b
=(2a+b-a-2b)[a-b-(b-a)/3]
=(a-b)/[4(a-b)/3]
=3/4

或者
2a+3ab-2b/a-ab-b
=[2(-3ab)+3ab]/(-3ab-ab)
=3/4[提问者认可]|赞同11|评论(1) 检举|2008-08-06 12:05sunnyjustin|六级分子分母都先除以ab得：
(2/b+3-2/a)/(1/b-1-1/a)=(-6+3)/(-3-1)=3/4赞同1|评论 检举|2008-08-06 12:05海船果心|三级由1/a-1/b=3得b-a=3ab
则2a+3ab-2b=a-b
a-ab-b=4/3(a-b)
所以原式=3/4赞同2|评论 检举|2011-02-24 21:51六棱心|八级从第一条件得出b-a=3ab,a-b=-3ab
a-ab-b=-4ab
2a+3ab-2b=-3ab
结果是四分之三赞同4|评论 检举|2012-02-11 14:53dreamqiran|二级/a-1/b=3,
(b-a)/ab=3
b-a=3ab
a-b=-3ab

(2a+3ab-2b)/(a-ab-b)
=[2(a-b)+3ab]/[(a-b)-ab]
=(-6ab+3ab)/(-3ab-ab)
=-3ab/(-4ab)
=3/4
参考资料：http://zhidao.baidu.com/question/229253442.html赞同2|评论