The first thing you must remember is that the product of matrices is done by multiplying rows by columns. For this case, the AB matrix is AB = [1 0 0; 0 1 0; (x + 1) 0 y] Equalizing the identity matrix we have AB = I [1 0 0; 0 1 0; (x + 1) 0 y] = [1 0 0; 0 1 0; 0 0 1] Therefore we have x + 1 = 0 y = 1 The values of x and y are x = -1 y = 1 the answer is X=-1 Y=1
