9. 如圖(九), D、 F 兩點在
【mathisthebest】評論
本題的 AC = 6 可以不用去管它∵ AD:DF:FB = 1:2:3∴ DE:FG:BC = 1:3:6設 DE = r,FG = 3r,BC = 6r,r ≠ 0BC = 6r = 4,r = 2/3FG - 3DE = 3r - 3r = 0Ans: (A)