input: Write a python function to determine the focal point of a parabola.  
  assert find_parabola_focus(5,3,2)==(-0.3, 1.6)  
  assert find_parabola_focus(9,8,4)==(-0.4444444444444444, 2.25)  
  assert find_parabola_focus(2,4,6)==(-1.0, 4.125)
output: def find_parabola_focus(a, b, c):
      x = -b / (2 * a)
      y = (1 - (b ** 2) / (4 * a) + c)
      return (x, y)