Question

如果a分之b=2分之3,且a≠2,那么a+b分之a-b=

Answer 1

(a-b)/(a+b)=(a+b-2b)/(a+b)
=1-2b/(a+b)
=1-2/(a/b+1)
=1-2/(2/3+1)
=-1/5

(x+1)/(y+1)+(y+1)/(x+1)
=(x²+2x+1+y²+2y+1)/(xy+x+y+1)
=[(x+y)²-2xy+2(x+y)+2]/(xy+x+y+1)
=(16+24-8+2)/(-12-4+1)
=34/(-15)
=-34/15

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Answer 2

(a-b)/(a+b)
=(a/b-1)/(a/b+1)
=(2/3-1)/(2/3+1)
= (-1/3)/(5/3)
= -1/5

追问

还有下面的那一道

Answer 3

-1/5,分子分母同时除以b，原式=（a/b-1)/(a/b+1)=(2/3-1)/(2/3+1)=-1/5

Answer 4

分子分母同时除以b，就出来了

Answer 5

3a=2b,a=2/3 b 则把a代入可得结果-1/5