Question

Consider the following matrix A, and let B = A−1. Find b31, b32, and b33. (i.e., find the entries in the third row of  A−1.

A = 1 1 -2
-9 -1 0
-2 -1 2

Answer 1

The result of operation A - 1 is:
0 0 -3
-10 -2 -1
-3 -2 1

which is equal to matrix B.

Looking at the third row we have:
b31 = -3
b32 = -2
b33 = 1
which are the entries in the third row of A - 1