∵四边形ABCD是平行四边形且点E在边BA的延长线上,∴DC∥BE.∴∠D = ∠FAE.而∠D=∠ECA,∴∠FAE = ∠ECA.在△EFA 和 △EAC 中,∵∠E = ∠E,∠FAE = ∠ECA（已证）,∴△EFA ∽ △EAC .∴FA / AC = EA / EC即：FA / 6 =...