How do you invert a 2x2 matrix?

Take a matrix A=(acbd), where a,b,c,d are numbers.

First find the determinant. This is ad-bc.

Now, rearrange the matrix to become (d-c-ba). Divide this by the determinant, to have A-1=1/(ad-bc)(d-c-ba). This is the inverse of A.

YP

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