题目

已知f（x）＝x2﹣4x+2，数列{an}是等差数列且单调递减，a1＝f（a+1），a2＝0，a3＝f（a﹣1），则数列{an}的公差为_____，数列{an}的通项公式为_____． 答案：【答案】﹣2 4﹣2n 【解析】首先由数列{an}是等差数列，可得，易得或3，数列{an}是等差数列且单调递减，舍去一个，易得公差和通项公式.因为数列是等差数列，所以，所以有，，解得或3，又因为数列是等差数列且单调递减，所以当时，公差为2不符合题意,舍去.当时，易得公差，，所以数列的通项公式任务型阅读理解：仔细阅读下面的短文并按要求完成后面的小题。(5小题，每小题2分，共10分) Playing  is serious business for children . In fact , it’s what they do best ! Ask them why they do it , and kids will probably say , “ Because it’s fun !” But it’s much more than that . It’s also good for them . 3.Studies show that from birth babies learning through play . They use their five senses to get know their new world . Touching allows them to discover how different things feel . Brightly colored toys and clothing help develop a baby’s sense of sight .When small children choose which toy to play with , they begin developing their abilities in making decisions .Children love toys that allow them to use their imagination .Sometimes an empty box is more fun than a high—tech toy . That’s because a box can become anything a child imagines it to be .Crayons , paints and Play-Doh (彩色塑泥) are also good because they allow children to create . Traditional building blocks teach important pre-math skills like problem—solving .4.Playing doesn’t become any less important once children start school . Many valuable lessons about life are learned on the school playground . Kids learn how to share , take turns and play by the rules .1. What can children do best in their childhood ?______________2. What kind of toys do children lover ?_______________________________________________.将短文译成汉语3_____________________________________4_____________________________________________5.请给短文拟一个适当的题目。___________________________