Have you eventriedto do this yourself? It's very straight forward.

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Since P must be a 2x2 matrix in order to be able to subtract 2P, write it as [tex]\begin{bmatrix}a & b \\ c & d\end{bmatrix}:

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Do the indicated calculations and you will have 4 separate linear equations for a, b, c, and d. For example, one equation is 1- 2a= -2. That's easy to solve.