Question

已知a-b分之a+b=2，求a-b-2(a-b)分之3(a+b)-a-b的值

Answer 1

因为a-b/a+b=2
所以a-b=2a-2b
a=3b
原式=a-b-2a+2b/3a+3b-a-b
=-a+b/2a+2b
=-3b+b/6b+2b
=-2b/8b
=-2/8
=-1/4

Answer 2

(a+b)/(a-b)=2

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

Answer 3

a-b-2(a-b)=-(a-b)
3(a+b)-a-b=3(a+b)-(a+b)=2(a+b)
所以a-b-2(a-b)分之3(a+b)-a-b
=2(a+b)/[-(a-b)]
=-2[(a+b)/(a-b)]
=-2*2
=-4

Answer 4

解:由a-b分之a+b=2 得 a+b=2a-2b
a-b-2(a-b)分之3(a+b)-a-b
=a-b-2a+2b分之3a+3b-a-b
= - (a-b)分之2(a+b)
将a+b=2a-2b代入得
- (a-b)分之2(a+b)
= - (a-b)分之2（2a-2b）
= -（a-b）分之4（a-b）
= -1分之4
= -4

Answer 5

2a-2b=a+b得a=3b
a-b-2(a-b)=-2b
3(a+b)-a-b=8b
a-b-2(a-b)分之3(a+b)-a-b=-4

Answer 6

-1/2