初三数学 由平行线截得比例线段 要详细过程!

Question

如题所述

Answer 1

∵ AE=BC
∴ CF/AE = CE/AC = CE/(AE+CE) = CE/(BC+CE) = CF/BC
3 / (BC+3) = 2 / BC
BC = 6
根据（1）的结论
DE/DB = CE/AC = CE/BC = 3/6 = 1/2