问题 选择题
方程
(x-2)2+y2
+
(x+2)2+y2
=10化简结果是(  )
A.
x2
25
+
y2
16
=1
B.
x2
25
+
y2
21
=1
C.
x2
25
+
y2
4
=1
D.
y2
25
+
x2
21
=1
答案

方程

(x-2)2+y2
+
(x+2)2+y2
=10表示动点M(x,y)到两个定点(±2,0)的距离之和为定值10=2a,

且10>2+2,由题意的定义可得:动点M的轨迹是椭圆,且b2=a2-c2=52-22=21.

可得椭圆的方程为:

x2
25
+
y2
21
=1.

故选:B.

单项选择题
句型转换

按要求改写下列句子。

1. Being a volunteer is great.(改为反意疑问句)

    Being a volunteer is great,________  ________?

2. You finish your homework. I will go to the park with you.(改为复合句)

                                                                

3."I'm listening to music," she said.(改为间接引语)

                                                                

4. Both of the boys are good at playing soccer.(改为否定句)

    ________of the boys ________good at playing soccer

5. Jim has been collecting shells for five years.(对画线部分提问)

                                                                    

6. We shouldn't talk loudly in the theater.

    We shouldn't smoke there, either,(改为同义句)

    We should________talk loudly________smoke in the theater.

7. It took them half a year to finish the work.(改为同义句)

    They________half a year in________the work.

8. I would like to go to the park tomorrow.(改为同义句)

    I ________ ________going to the park tomorrow.

9. He gets on well with his classmates.(对画线部分提问)

                                                                    

10. John's grandfather died ten years ago.(改为同义句)

      John's grandfather has________ ________for ten years.