$19\mathrm{.}1$: Use three nodes $x_0=2,x_1=2\mathrm{.}5,$ and $x_2=4$ and formula stated in class to find the second$-$degree

interpolation $({}_2(x))$ for $f(x)=\frac{1}{x}$ by hand. Then, evaluate $($a$){}_2(3),($b$)$ absolute error: $|f(3)-{}_2(3)|,$

$($c$){}_2(1),($d$)$ absolute error: $|f(1)-{}_2(1)|.$

$($e$)$ Modify the functions: demoGasLag.m and mylagrint.m $($available in canvas$)$ to graph $y={}_2(x)$ and

nodes: $(x_0,f(x_0)),(x_1,f(x_1)),$ and $(x_2,f(x_2))$ in a same graph.