∵在△ABC中,BD=2DC,∴CD= 1 3 BC,∴S△ACD= 1 3 S△ABC= 1 3 ×42=14,∵CE=2EA,∴AE= 1 3 AC,∴ S△ABE S△ABC = AE AC = 1 3 , S△AEF S△ABE = EF BE = 1 7 ,∴ S△AEF S△ABC = 1 21 ,∵S△ABC=42,∴S△AEF= 42 21 =2.