3D graphing the parameter space

Question

3D parameter spaceHi there I was given the equation X'= [a,b c,0]X and was asked to graph the parameter space as "a" changes. I tried but I'm not completely sure this is what they were looking for. I put the equation 4D-T^2<0 or 4(Determinant)-(Trace)^2 < 0, into the graph then sectioned off the quadrants where D is positive and negative. I understand how the system changes with the fluctuation of "a" when looking at the bc-plane but I can't really conceptualize 3D. Is it just adding "a" as an axis? and if so how do I code that?