Let \(\mathbf{P}\) be the \(2\times 2\) matrix that projects vectors onto \(\mathbf{u} = \begin{pmatrix}2\\ -1 \end{pmatrix}\). That is, \(\mathbf{P} \bold{v} = \operatorname{proj}_{\bold{u}} (\bold{v}) = \text{Projection of $\mathbf{v}$ onto $\mathbf{u}$}\)
Use your answers from part (a) to figure out \(\mathbf{P}\).
