http://answers.yahoo.com/question/index;_ylt=Ak.iBxE2OXu.CQvAY7qdzDwjzKIX;_ylv=3?qid =20080708170131AAjrUst


The question is :Let A be an nxn matrix. Is it possible for A^2 + I = 0 if n is odd? Where n is even?



I still don't understand this part : [ det(A) ]^2 = det( -I )

what do you do after that ^
and
why is it that the det(-I) = 1 when n is even and -1 when n is odd

isn't det (-1)= -1 always? What did he mean?