Exercise 4.3.22

The least squares equation is $\left[\begin{array}{cc}\hfill 5& \hfill 0\\ \hfill 0& \hfill 10\end{array}\right]\left[\begin{array}{c}C\hfill \\ D\hfill \end{array}\right]=\left[\begin{array}{c}\hfill 5\\ \hfill -10\end{array}\right]$. Solution: $C=1,D=-1$. The best line is $b=1-t$. Symmetric $t$ ’s $\Rightarrow$ diagonal $A^{T}A\Rightarrow$ easy solution.