Exercise 4.3.2

This $Ax=b$ is unsolvable $\left[\begin{array}{c}\hfill 1\\ \hfill 5\\ \hfill 13\\ \hfill 17\end{array}\right]$; When $p$ replaces $b$ to $p=Pb=$

$\hat{x}=\left[\begin{array}{c}1\hfill \\ 4\hfill \end{array}\right]$ exactly solves $A\hat{x}=p$.