Matrix algebra & applications

               2 1 0                   1 0 1Let A = [ 1 0 1 ] and B = [ 2 0 1 ]                0 3 0                  0 1 1 Find the matrix X such that (2X + A)-1 = B.

If A is a 2 x 2 matrix such that AAT (Transpose) = 0, then A = 0.

I used substitution method and got one answer then used matrix method and got a completely different answer