3/(a+b)=a/(b+c)=b/(a+c)=k则k的值为( )A.1/2 B.1 C.-1 D.1/2或-1
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3/(a+b)=a/(b+c)=b/(a+c)=k则k的值为( )A.1/2 B.1 C.-1 D.1/2或-1
3/(a+b)=a/(b+c)=b/(a+c)=k
则k的值为( )
A.1/2 B.1 C.-1 D.1/2或-1
3/(a+b)=a/(b+c)=b/(a+c)=k则k的值为( )A.1/2 B.1 C.-1 D.1/2或-1
c=(a+b)k
a=(b+c)k
b=(a+c)k
将上式相加,a+b+c=2k(a+b+c)
a+b+c=0时,k=a/(b+c)=a/(-a)=-1
a+b+c≠0时,2k=1,k=1/2
选D
D
第一个3,应该是c
-1
展开:a^2+ac=b^2+bc==>
(a-b)(a+b)=c(b-a)==>c=-a-b
代入可得