∵DG//EF//BC
∴△ADG∽△AEF∽△ABC
∵S△ADG=S梯DGFE=S梯EFCB
∴S△ADG:S△AEF:S△ABC=1:2:3
∴AD:AE:AB=DG:EF:BC=AG:AF:AC=1:根2:根3
∴AD:DE:BC=1:根2-1:根3
∵DG//EF//BC
∴△ADG∽△AEF∽△ABC
∵S△ADG=S梯DGFE=S梯EFCB
∴S△ADG:S△AEF:S△ABC=1:2:3
∴AD:AE:AB=DG:EF:BC=AG:AF:AC=1:根2:根3
∴AD:DE:BC=1:根2-1:根3