若3/(a+b)=a/(b+c)=b/(a+c)=k,则k的值为( )
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若3/(a+b)=a/(b+c)=b/(a+c)=k,则k的值为()若3/(a+b)=a/(b+c)=b/(a+c)=k,则k的值为()若3/(a+b)=a/(b+c)=b/(a+c)=k,则k的值为
若3/(a+b)=a/(b+c)=b/(a+c)=k,则k的值为( )
若3/(a+b)=a/(b+c)=b/(a+c)=k,则k的值为( )
若3/(a+b)=a/(b+c)=b/(a+c)=k,则k的值为( )
1/2
c/(a+b)=a/(b+c)=b/(a+c)=k
(a+b)/c=(b+c)/a=(a+c)/b=1/k
1+(a+b)/c=1+(b+c)/a=1+(a+c)/b=1+1/k
(a+b+c)/c=(a+b+c)/a=(a+b+c)/b=(k+1)/k
a+b+c=0,或,a=b=c
a+b+c=0时,(k+1)/k=0,k=-1
a=b=c时,k=c/(a+b)=c/2c=1/2
所以,k=-1,或,1/2
3/2
3/(a+b)=a/(b+c) => a^2+ab=3b+3c
3/(a+b)=b/(a+c) => b^2+ab=3a+3c
想减得 a^2-b^2=3b-3a => (a+b)*(a-b)=-3*(a-b) => a+b=-3
=> k=3/(a+b)=-1
a=b=c时 k=1/2