input: Write a function to combine two given strings and reverse the resulting string in Python. The function should return the reversed combined string.
  
  assert reverse_combined("Hello ", "world!")=="!dlrow olleH"
  assert reverse_combined("Python", "Programming")=="gnimmmargorPnohtyP"
  assert reverse_combined("Open", "AI")=="IA nepO"
  assert reverse_combined("", "")==""
  assert reverse_combined("Single", "")=="elgniS"
output: def reverse_combined(str1, str2):
      return (str1 + str2)[::-1]