ive been dieing over this for the past three hours - i just cant do the damn thing. please try and solve my equasion for variable 'c'. Even if you cant, please offer some advice.

im not particulary interested in the answer.. but how to get to it. i already know the answer (various calculators on the web).

the equation is:

ab-4ca-4cb+12c^2=0

thanko mucho