参考充分条件A^2=AA^2=0.5(B+E)*0.5(B+E)=0.25(B+E)(B+E)=0.25(B^2+2B+E)=0.5(B+E)B^2+2B+E=2(B+E) 得 B^2=E必要条件A=0.5(B+E)得2A-E=B 两侧都乘以自身(2A-E)(2A-E)=B^24A^2-4A+E=B^2=E 得4A^2-4A=O(0矩阵)得A^2=A...
