题目

A poor farmer had a friend who was famous for the wonderful apple tree he grew.     One day, his friend gave the farmer a young apple tree and told him to plant it. The farmer was pleased with the gift, but he did not know where to plant it.     He was afraid that if he planted the tree near the road, strangers would steal the fruit. If he planted the tree in one of his fields, his neighbors would come at night and steal some of the apples. If he planted the tree near his house, his children would take the fruit. Finally he planted the tree in his wood．But without sunlight and good soi 如图，A、F、C、D在同一条直线上，AB＝DE，BC＝EF，AF＝CD，求证：BF＝CE