题干

已知直线l:y=ax+1﹣a(a∈R).若存在实数a使得一条曲线与直线l有两个不同的交点,且以这两个交点为端点的线段长度恰好等于|a|,则称此曲线为直线l的“绝对曲线”.下面给出四条曲线方程:①y=﹣2|x﹣1|;②y=x2;③(x﹣1)2+(y﹣1)2=1;④x2+3y2=4;则其中直线l的“绝对曲线”有(  )

A:①④

B:②③

C:②④

D:②③④

上一题 下一题 0.0难度 选择题 更新时间:2014-08-18 10:46:01

答案(点此获取答案解析)

D

同类题3

任务型阅读

Question: I have been learning English for about 7 years. ____ And I still can't make myself understood in English. However, I love learning English. How can I learn English well? Please help me.

Answer: Many people have asked me this question. ____ Here I will give you several tips for learning English.

●____

    First of all, you must want to learn. If you are not interested in learning English, no class will help you and no book will help you. So you have to be honest with yourself. Ask yourself, “Do I really want to learn English?” If you can't answer “yes” to this question, it is better for you to set English aside until you're ready and willing to learn.

● Set goals (目标).

    To learn English well, you must set some goals. ____ It will also help you to see your progress. Ask yourself, “What are my goals? What areas would I like to improve?” Think about what your goals are, and review once in a while to see that you are making progress toward your goals.

● Practice, practice, and practice.

    After you have set your goals, you have a better idea of what you need to practice. Just like the athlete whose goal is the Olympics must train daily, you as a language learner must practice language every day to make progress toward your goal. ____

A. Want to learn.

B. I think it is not easy to learn it well.

C. Make friends with some Americans online.

D. Reading is a very good way to learn new words.

E. The answers are as different as the people asking the question.

F. The more you practice, the more progress you will make.

G. Having goals will help you remember what areas you want to work on.