题目

若直角坐标平面内的两点P,Q满足条件:①P,Q都在函数y=f(x)的图象上; ②P,Q关于原点对称,则点对(P,Q)是函数y=f(x)的一个“友好点对”(点对(P,Q)与(Q,P)看作同一个“友好点对”).已知函数f(x)=则此函数的“友好点对”有对. 答案：2【解析】根据题意:“友好点对”,可知, 作出函数y=-2x2+4x-1(x≥0)的图象关于原点对称的大致图象, 同一坐标系内作出函数y=-的大致图象如图: 观察图象可得,它们在x<0时的交点为A,B,个数是2. 即f(x)的“友好点对”有2个.One year, my school report made my parents angry. On Christmas Eve, all the presents were stolen, along with our TV. My parents told me that there were no presents because Santa was very angry with my behavior over the past year. The next year on Christmas Eve I slept downstairs with a plastic sword waiting for Santa to make sure that he didn't steal the new TV. The next morning, when I woke up, I saw Santa standing there. As soon as I saw that there were no presents, I grabbed my plastic sword and ran at him, shouting angrily: "THIEF! THIEF!" Jack When I was young, we always had a specific room for the Christmas tree. My mom never really liked the location, so one year she moved the tree into another room. I was convinced that Santa would not know where the tree was and would get lost in our house. I was worried that he would be mad and put me on the "bad" list and would not give me any gifts because he couldn't find the tree. I came up with the idea to make signs leading from the fireplace to the tree. They said things like: "Tree this way" or "Santa, put the gifts over here." When my big brother saw them he began to laugh his head off. Lucy Does everyone remember going to the mall and sitting on Santa’s lap to have his picture taken at Christmas time? Well, I used to think that if I did that, Santa would get mad bcause he would have to go all around the world and give every kid the chance to have his picture taken with him. Of course his lap would hurt and he would be very fired. I thought he might keep a copy of the picture and that would be how he decided who would be on his naughty list. My mom couldn't get me onto Santa's lap until she made him promise I wouldn't end up on his naughty list. Lydia小题1:The real reason why Jack's TV was taken away is that ______________.A．his parents were too carelessB．his parents thought he had watched too much TVC．Santa Claus was not satisfied with Jack’s behaviorD．Santa gave the TV to another child as a present小题2:Which of the following is NOT one of the reasons why Lucy didn't want the tree to be moved?A．Santa would not know where the tree was.B．Santa would be angry and would not give her any gifts.C．Her big brother might laugh at her.D．Santa might think she was a "bad" child.小题3:We can learn from the third story that _______________.A．Lydia’s mother was very Strict with herB．Lydia believed in Santa when she was youngC．Lydia was naughty when she was youngD．Lydia liked taking pictures with Santa小题4:Why didn't Lydia want to take pictures with Santa?A．She was afraid that Santa would get mad with her.B．She was afraid that Santa would get too tired and hurt himself.C．She disliked the idea that Santa would keep a copy of her picture.D．She feared that she would appear in the Santa's naughty list.