题目

阅读理解 Every weekend Tim's mom goes to a supermarket in the Green Street．Tim loves to go with her．Tim's favorite store is next to the supermarket．It is Billows Book Store．Mom goes shopping in the supermarket and Tim goes to the bookstore．Tim's favorite section(部分)is the sports section for children．It has all kinds of books about sports．It also has many new magazines(杂志)．They tell everything about sports． Tim likes sports and he spends (花)a lot of time reading the books and magazines in this section．He likes the section with music books， too．Tim always wa若椭圆方程是x218+y29=1，直线AB过椭圆右焦点，且OA⊥OB，则AB的方程为 ．