Hi NewtoMath,

To find the inverse of a (2x2) matrix, interchange the elements in the leading diagonal, change the signs of the elements in the other diagonal and divide by the determinant of the matrix.

We have

So,

clearly I tried to find out what a regular matrix was. There are various definitions to do with stochastic matrices. The most suitable was that a regular matrix is one for which AB = BA, which is true in this case.