Chapter 5.4, Problem 23E

Find the least-squares solution $\stackrel{\to }{x}*$ of the system
$A\stackrel{\to }{x}=\stackrel{\to }{b}$ , where $A=\left[\begin{array}{cc}1& 1\\ 2& 8\\ 1& 5\end{array}\right]$ and $\stackrel{\to }{b}=\left[\begin{array}{l}1\\ -2\\ 3\end{array}\right]$
Explain.