A is a 2x2 matrix, a12=a21=0, a11 does not equal 0, a22 does not equal 0.

Show that A is regular and find inverse of A

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- March 21st 2010, 05:38 AMNewtoMath[SOLVED] Matrices
A is a 2x2 matrix, a12=a21=0, a11 does not equal 0, a22 does not equal 0.

Show that A is regular and find inverse of A - March 21st 2010, 12:19 PMs_ingrammatrices
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. - March 21st 2010, 10:01 PMNewtoMath
Hey thanks ingram! can't believe I didn't figure what "a12=a21=0" meant (Dull)

In my book it means to be a regular square matrix when there is an existing inverse or determinent, like when it doesn't equal zero in which case it's a singular.

Thanks again.