If ax = b, then (a-1)ax = (a-1)b, or x = (a-1)b (except when a is zero).
The value (a-1) is the inverse of a, and all non-zero real numbers have an inverse. It would be nice to have a similar idea for square matrices.
Say that
Ap = q
for column vectors p and q and n×n matrix A .
If all know are A and q, is it possible to figure out what p is? For example, say that you know that
1 2 0 1p = 5 2
Try to figure out p from the following. Keep changing the elements of p until the result is q.