4y'' + 12y' +9y = 0
i) Compute general solution in terms of real functions.
ii) From roots of characteristic equation, find whether each critical point of corresponding dynamical system is assymptotically stable, stable, or unstable, and categorize it as to type.
iii) Use general solution obtained in part(a) to determine a 2 parameter family of trajectories x=x1i+x2j=yi+y'j of corresponding dynamical system. Then draw by hand to sketch the phase portrait comprising any straight line orbits, from the family of trajectories.