k=3c/a+b+2c=3a/b+c+2a=3b/a+c+2b应该是下列写法吧：k=3c/(a+b+2c)=3a/(b+c+2a)=3b/(a+c+2b)当a+b+c≠0时根据等比定理得：k=(3a+3b+3c)/[(a+b+2c)+(b+c+2a)+(a+c+2b)]=3(a+b+c)/4(a+b+c)=3/4当a+b+c=0时a+b=-c所以k=...