Example.
$y''-y'-2y=0$
has the reduced 1st order system:
$y'=v$
$v'=2y+v$
this 1st order system has the general solution:
$y=C_1\begin{bmatrix}1/2 \\ 1\end{bmatrix}e^{2t}+C_2\begin{bmatrix}-1 \\ 1\end{bmatrix}e^{-t}$
How can I use the general solution above to draw a direction field and solution curves? I know how to do it for first order ODEs only and can't find anything for second order ODEs. Thanks.