Parabol, The Fourth Eye

For $a² > 4b$ , let the function $S(a,b)$ be the area of the quadrilateral defined by four selected points of the parabola $y =x²+ax+b$ , respectively the y-axis interception, the first x-axis interception, the vertex and the second x-axis interception.

The value of the expression

$\displaystyle \dfrac{S(-2,-4)}{S(2,-4)}$

can be written as an irreducible fraction $\dfrac{m}{n}$ . Evaluate $m+n$ .