搜题请搜索小程序“爱下问搜题”
问题 填空题
已知P为
x2
4
+
y2
9
=1，F1，F2为椭圆的左右焦点，则PF2+PF1=______．
答案

∵

x2
4
+
y2
9
=1，F1，F2为椭圆的左右焦点，

∴根据椭圆的定义，可得|PF2|+|PF1|=2×2=4

故答案为：4

填空题

根据所给汉语提示写出单词，每空一词。

1. _____ (土豆) are my favourite food. I almost eat them every day.

2. The shopping mall sells food from different _____ (国家).

3. Eddie is a very_____ (懒惰的) dog. He is sleeping all the time.

4. The baby has four _____ (牙齿).

5. My father spends half an hour _____ (完成) washing his car.

6. Simon likes to wear _____ (色彩艳丽的) trainers.

7. The room is small, _____ (但是), it's tidy.

8. I like playing basketball  _____ (在……之前) I go home after school.

查看答案
单项选择题

患者，女，58岁。左侧腰周出现绿豆大水疱，簇集成群，累累如串珠，排列成带状，疼痛较重，舌苔薄黄，脉弦数。其诊断是（）

A.接触性皮炎

B.药物性皮炎

C.蛇串疮

D.热疮

E.湿疮
查看答案