function parabola( a, b, c)
%PARABOLA Summary of this function goes here
%   Detailed explanation goes here

    rts = sort(roots([a b c]));
    x1 = rts(1);
    x2 = rts(2);
    d = (x2 - x1)/2;
    x = rts(1)-d:.1:rts(2)+d;
    y = a*x.^2 + b*x + c;
    plot(x, y);
end