搜题请搜索小程序“爱下问搜题”
问题 解答题
化简：
1
3
+1
+
1
5
+
3
+
1
7
+
5
+…+
1
2n+1
+
2n-1
______．
答案

原式=

3
-1
2
+
5
-
3
2
+
7
-
5
2
+…+
2n+1
-
2n-1
2
，

=

3
-1+
5
-
3
+…+
2n+1
-
2n-1
2
，

=

2n+1
-1
2
．

故答案为：

2n+1
-1
2
．

单项选择题

When I was young, my parents ran a snack bar in our small town.One evening in early April, my mother told me to fill in at the snack bar (1) a worker who had the flu. I told her I would mess it up, (2) I had never worked at the bar before. I (3) that instead of making money, I would end up owing it."You can do it," said my mother," (4) , you won’t get much business until lunch. ""But I’ll never remember the orders, and I’m no good (5) money. Please, Mom, don’t (6) me."Then I’ll help you", she said.I shrugged my shoulders. I thought my mother’s (7) was a bad one, but I (8) .When I got to the bar the next day, I found my mother was (9) . Because the weather that day was rainy and cold, people wanted hot snacks and drinks. (10) , I was really slow at taking the orders and making change. The line of people grew, and everybody seemed (11) , I was so nervous that my hands shook, and I (12) a cup into pieces. What a mess! Then my mother came to (13) me, and she also showed me how to make (14) . If someone gave me $ 5 for something that cost $ 3.25, I handed over (15) quarters and a dollar and said, "75 cents makes four dollars, plus one dollar makes five. " Things went more (16) after that.By the end of the day, I could remember orders, (17) the bill, and make change quickly with a smile. I was even a little (18) when the sun came out and dried up business. My mother said she was proud of me, and when she (19) that I work at the snack bar again next year, I did not even shrug. I was too busy (20) the restaurant I would open one day.

 

第（9）空应选择（）

A．angry

B．sad

C．wrong

D．ashamed
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单项选择题

采用等渗盐水补充重度等渗性缺水的丧失量可致()

A．良好的治疗效果

B．水中毒

C．氯化钠过高

D．血氯过高

E．血钠过高
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