题目

Dear Amy, I couldn’t read the letter from you until today because I was too busy. I’m sorry to hear about your illness, but I’m glad you’re feeling better. This is really a moving(动人的) story — the young man didn’t know you, but he gave part of his liver(肝脏) to you. It’s very kind of him. You shouldn’t care too much about your weight(重量). I’m happy you won’t take those weight-loss pills(减肥药). From your photo I can see you are now looking very well in the hospital. Nothing is more important than health. Your doctor’s advice is very good — ex正方形纸片ABCD和BEFG的边长分别为5和2，按如图所示的方式剪下2个阴影部分的直角三角形，并摆放成正方形DHFI，则正方形DHFI的边长为    ．