input: Write a python function to find the maximum and minimum numbers in a list.
  assert find_max_min([9,6,7,11,14,5])==[5, 14]
  assert find_max_min([3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5])==[1, 9]
  assert find_max_min([0, -1, -2, -3, -4, -5])==[-5, 0]
  assert find_max_min([100, 200, 300, 400, 500])==[100, 500]
  assert find_max_min([7])==[7, 7]
output: def find_max_min(lst):
      return [min(lst), max(lst)]