The matrix is singular! Hint: read the error message. There is no solution.
Worse, there could NEVER be a solution, even if the matrix was not singular!!!!!!!
A is a 5x5 matrix. b is a 4x1 vector.
There exists no possible vector x such that A*x will be a 4x1 vector. NOT gonna happen. EVER. So asking for working code to do the impossible is a waste of CPU cycles. Trying to do that with a singular matrix? Even sillier.
