Plot the region of absolute stability of the method
$y_{n+2}-y_n=\frac{1}{2}h(f_{n+1}+3f_n)$
where $f_n=(y_n,t_n)$.
The only thing I can think of to do is absolute stability with the test equation,
$y'=\lambda y$
$|y_n|\leq |y_{n+1}|$
The problem I am encountering is I have $y_{n+2}$ but we also have $y_{n+1}$.
So the reason why I was taking this approach was to see if I could compute it by hand and then plot it on Matlab. Considering that I can't plot this by hand because I don't know what method to use,
How would I plot the region of absolute stability of the method in Matlab?