问题 填空题

若不等式x2+2x+a≥-y2-2y对实数x,y都成立,则实数a范围是

A. a≥0

B. a≥1

C. a≥2

D.a≥3

答案

答案:C

题目分析:由题意可知,不等式x2+2x+a≥-y2-2y对实数x,y都成立,那么可知a≥-y2-2y-x2-2x

而对于-y2-2y-x2-2x=-(y+1)2-(x+1) 2+22,因此可知,a的取值范围就是右边表达式的最大值即可,即为a≥2,选C.

点评:解决不等式的恒成立问题,主要是利用分离参数的思想,结合不等式的性质和函数的性质等来分析其取值范围即可,属于中档题。

阅读理解

Habits,whether good or bad,are gradually formed when a person does a certain thing again.He is driven by some unseen force to do the same thing repeatedly, and then a habit is formed.Once a habit is formed,it is difficult,and sometimes impossible,to get rid of.It is therefore very important that we should pay great attention to the formation of habits.Children often form bad habits, some of which remain with them as long as they live older. Persons also form bad habits lasting as long as they live,and sometimes become ruined by them

There are other habits which,when formed in early life,are of great help.Many successful men say that much of their success has something to do with certain habits in early life,such as early rising,honesty and so on.

Among the habits which children should not form are laziness,lying,stealing and so on.These habits are all easily formed.Unfortunately older persons often form habits which could have been avoided.

We should keep away from all these bad habits,and try to form such habits as will be good for ourselves and others.

小题1:      are formed little by little.

A.Good habits

B.Bad habits

C.Both good habits and bad habits

D.Neither good habits nor bad habits小题2:The underlined word“them”in the first paragraph refers to_______.

A.bad habits

B.good habits

C.children

D.other persons小题3:Generally speaking, it’s difficult for one______ and easy for them______ which should be avoided.   

A.to form bad habits;to form good habits

B.to form good habits;to form bad habits

C.to form such habits as wilI be good;to get rid of bad habits

D.to get rid of bad habits;to form good habits

单项选择题 A1/A2型题