The equation of parabola is
For point (-1,-9), equation of parabola is
For point (1,7), equation of parabola is
For point (-6,-14), equation of parabola is
So we have three equations , which are
Subtracting first two equation will give
Subtracting second and third equation gives
Substituting 8 for b, we will get
back substituting 8 for b and 1 for a, we will get
So we have
Therefore required equation is