问题 解答题
抛物线y=ax2+bx+c上部分点的横坐标x,纵坐标y 的对应值如表所示.
x

-3
-2
-1
0
1

y
…[
-6
0
4
6
6

 
 
 
 
 
 
 
 
 
给出下列说法:①抛物线与y轴的交点为(0,6); ②抛物线的对称轴是在y轴的右侧;
③抛物线一定经过点(3,0);  ④在对称轴左侧,y随x增大而减小.从表中可知,下列说法正确的个数有           
答案

3

题目分析:根据表中数据和抛物线的对称形,可得到抛物线的开口向下,当x=3时,y=0,即抛物线与x轴的交点为(-2,0)和(3,0);因此可得抛物线的对称轴是直线 ,再根据抛物线的性质即可进行判断.根据图表,当x=-2,y=0,根据抛物线的对称形,当x=3时,y=0,即抛物线与x轴的交点为(-2,0)和(3,0);∴抛物线的对称轴是直线,根据表中数据得到抛物线的开口向下,∴当时,函数有最大值,而不是x=0,或1对应的函数值6,并且在直线的左侧,y随x增大而增大.所以①③④正确,②错.2+bx+c的性质

点评:此类试题属于难度很大的试题,考生解答此类试题时一定要细心的分析求解,且不可急躁,把握好抛物线y=ax2+bx+c的性质。

阅读理解

Mount Kilimanjaro is the highest mountain in Africa and one of the largest free-standing mountains in the world, and some say, the most beautiful place on the earth!

The mountain towers 15,000 feet above the plains. Mount Kilimanjaro is in Tanzania and it covers an area of 60 miles long and 40 miles wide. Kilimanjaro is an extinct volcano(死火山), with 3 peaks. Kibo is the highest one in the center.

Because of Kilimanjaro’s great height, the mountain influences its own weather. Winds incoming from the Indian Ocean are stopped upward by the mountain and drop their moisture(湿气) as rain and snow. People have planted coffee, corn, and other crops on the lower slopes(斜坡).

Mount Kilimanjaro now attracts many thousands of walkers each year. Because of a temperature rise in recent years, the beautiful snow cap of Kilimanjaro is retreating(消退)fast. A research said that the white snow on the mountain might be gone in 15 years. What a pity!

小题1:The writer is worried about Mount Kilimanjaro’s ________.

A.great height

B.extinct volcano

C.rainforests

D.white snow cap小题2:Mount Kilimanjaro is __________

A.the highest mountain in the world

B.an active volcano

C.a free-standing mountain

D.15,000 feet above the sea level小题3:The snow on the mountain comes from ________.

A.the Indian Ocean

B.the Pacific Ocean

C.the Atlantic Ocean

D.the Red Sea小题4:_________ influences the mountain’s own weather.

A.Rain and snow

B.Its great height

C.Crops

D.The moisture小题5: People should _______ to stop the mountain’s snow cap from melting.

A.save the water of the Indian Ocean

B.protect the environment

C.not visit Kilimanjaro

D.not plant crops on the mountain

问答题