Mathematics is a compulsory course to solve problems.
Solution: First of all, it is a set, so A is not equal to ac, so C is not equal to 1~. Then let A=B and a=a be determined, so let a+b a+2b correspond to ac ac2. If a+b=ac a+2b=ac2, then c= 1 is invalid. If a+b=ac2 a+2b=ac, then calculate c= 1 or-1/2. Excluding c= 1, then c=- 1/2. Follow-up: If a+b=ac2 a+2b=ac,