题目若AB=BA,AC=CA,证明:A,B,C是同阶矩阵.且A(B+C)=(B+C)A,A(BC)=(BC)A若AB=BA,AC=CA,证明:A,B,C是同阶矩阵.且A(B+C)=(B+C)A,A(BC)=(BC)A题目解答答案