图甲是人的眼球结构示意图，图乙是某校八年级探究性学习小组同学在复习《人体对周围世界的感知》一节时，进行的“模拟眼球成像原理”实验图．请认真观察图并分析回答下列有关问题
若分式方程xx-4=2+ax-4有增根，则a的值为 （ ）
Hello! I am Joy. I'm a girl. I'm eleven. I'm in Class Eight, Grade Seven. This is my friend, Joan. She is twelve. She is a high school student(中学生). She is in Class Seven, Grade Eight. My English teacher is Miss White, but her English teacher is Miss Green. Look(看)！That's my mom. She's a Chinese(语文, 中文) teacher.
设2m＞2n＞4，则logm2与logn2大小关系是____
在等边△ABC中，CD是∠ACB的平分线，过D作DE∥BC交AC于E，若△ABC的边长为a，则△ADE的周长为 ( )
