Solution: According to the meaning of the question, we can add 2a+b=ck2b+c=ak2c+a=bk to get 3A+3B+3C = K (A+B+C) 3 = K (A+B+C) because a+b+c≠0, K =

Method 2 because a+b+c≠0, 2a+b\c=2b+c\a=2c+a\b=k, according to the proportional property (2a+b+2b+c+2c+a)/(a+b+c) = k3 (a+b+c