Let $$A = \left[\begin{array}{cc} 3 &6\cr 0 &3 \end{array}\right].$$ If possible, find an invertible matrix $P$ so that $D = P^{-1} A P$ is a diagonal matrix. If it is not possible, enter the identity matrix for $P$ and the matrix $A$ for $D$. You must enter a number in every answer blank for the answer evaluator to work properly.

$P =$ $\left[\Rule{0pt}{2.4em}{0pt}\right.$$\left]\Rule{0pt}{2.4em}{0pt}\right.$.

$D =$ $\left[\Rule{0pt}{2.4em}{0pt}\right.$$\left]\Rule{0pt}{2.4em}{0pt}\right.$.

Is $A$ diagonalizable over $\mathbb{R}$? choose diagonalizable not diagonalizable Be sure you can explain why or why not.