问题 解答题

若三个数成等差数列,其和为15,其平方和为83,求此三个数.

答案

由题意设三个数分别为a-d,a,a+d,则

(a-d)+a+(a+d)=15,(a-d)2+a2+(a+d)2=83,

解得a=5,d=±2.

所以这三个数分别为3、5、7;或7、5、3.

阅读理解

阅读理解。

     There was an old pear tree in a man's garden. In the past, the tree fruited

every year, so the man would get many pears. But now, the tree got old. There were no more pears for the man. So the ungrateful(忘恩负义的) man

decided to cut the tree down. When he walked to the tree with an axe(斧子)

in his hand, the tree said to him, "Please don't cut me down. I have brought so many pears for you in the past years. Now I only have a short time to live."

"I'm sorry. I have to do so," the man said, "because I need something to make a chair." Then he began to wave his axe. At that moment, a bird in the old tree said to him, "Don't cut it down! Every time you go out and your wife feels

lonely(寂寞的), she will come out to the garden and sit down under the tree

to enjoy its cool shade(树荫), and I sing songs to make her happy. We give

much pleasure(愉快) to your wife when you are away from home."

     The man didn't listen to the bird and drove(驱赶) it away. When he was

about to cut the tree, some bees flew out of it and said, "Listen! If you agree

not to kill this tree, we will give you delicious honey every day. Would you

please leave the tree with us?"

     The man got moved(感动). He said, "You are so kind to the tree, although it has become old. Now I see that I shouldn't cut it down. It has done so much to me and my wife. Let the tree stay here, and let the bird continue to sing

songs here." With these words, the man left. And the old tree lived there to its last day.

1. Which can be the best title of the story?

A. The Singing Bird

B. The Man's Wife

C. The Old Tree

D. The Kind Bees

2. Which is the most important reason(理由) for the man to cut down the

tree?

A. The tree was getting old.

B. The man needed wood to make a chair.

C. The tree didn't give any shade.

D. The man couldn't get any pears from it.

3. What made his wife happy when the man was not at home?

A. The tree and its shade.

B. The bees and their honey.

C. The bird and its songs.

D. The tree and the bird.

4. In the story, the word "continue" means "     ".

A. 再一次开始

B. 继续

C. 表演

D. 停止

5. What can we learn from the story?

A. People should never be ungrateful.

B. Good wood(木头) comes from pear trees.

C. Old people are kind and friendly.

D. Birds and bees are always helpful.

单项选择题