M matlabnoob Nov 2009 75 0 May 11, 2010 #11 HallsofIvy said: In general ABA is NOT equal to B! And A(ACA)A'= (A^2)C(AA') which is equal to (A^2)C only if AA'= I which is not always true. Click to expand... thank you both for your help(Wink) why isnt this always true? if and only if say AA' = I ... it makes sense for it to be true right??