The vertices of the triangle are A(-8,5), B(-15,-19) & C(1,-7).

Hence AB = 25, BC = 20 & CA = 15.

 

Now theres a prop of angle bisector that it divides the opposites side in the ratio of its arms. Hence AD divides BC in the ratio 5:3.

 

Hence, D(-5,-23/2).

Now, we can write the equation of AD in two point form.

It is (-13/3)x + 2y - (5/3) = 0

 

Hence a = (-13/3) and c = (-5/3)