单项选择题
设A,B均为n阶方阵,满足AB=BA,则下列等式不成立的是()
A.(A+B)(A-B)=A2-B2B.(A+B)2=A2+2AB +B2C.(A-B)2=A2-2AB +B2D.|A|+|B|=|A+B|
A.AB.BC.CD.D
A.A+IB.A-3IC.A+3ID.A-I