show that b is inverse of a

Question

a=[-1 1 -3] [2 1 -1]
[2 -1 4] b= [0 1 2]
[-1 1 -2 ] [-1 0 1]
i got ab = to [1 0 0 ]
[0 1 0]
[0 0 1] and for ba i got [1 0 -4]
[0 1 8]
[0 0 5] so there is not a inverse is this right

Answer 1

I don't understand how you are multiplying your matrices, but I found the inverse of matrix "a" to be
-3 1 -2
10 -2 7
4 -1 3

and I got ab to be equal to ba