For 2 x 2 matrices A, B and I, if A + B = I and 2A - 2B = I, then A equals __________.
Matrix C =
A
-A
Null matrix
The number of all possible matrices of order 3 × 3 with each entry 0 or 1 is
27
18
81
512
adj (AB) - (adjB) (adjA) =
adj A - adj B
I
0
adj A + adj B
A2 + B2
A2 + B2 + 2AB
A2 + B2 + AB - BA
A2 + B2 + AB + BA
