题目

已知为常数，，且，方程有两个相等的实数根.（1）求的解析式.（2）是否存在实数，使在区间上的值域是？如果存在，求出的值；如果不存在，请说明理由. 答案：【答案】（1）（2）存在，，，详见解析【解析】(1)利用,可代入方程得一组关于的方程,再根据方程有两个相等的实数根易得二次函数判别式为0即可算出.(2)易得对称轴为直线,故讨论区间与对称轴的位置关系,分,,三种情况进行讨论.（1）由,方程有两个相等的实数根,所以即判别式为0,得,解得.∴.（2）由（1 假如你叫Gina，是旅行社的工作人员，刚收到一封咨询邮件，请你根据来信，运用本学期所学的英语知识给Wang Ming回复一封邮件，从Sydney, Hawaii，Beijing和Taian中选一个或2个符合要求的地方，向他提出建议。要求不少于80词，可适当发挥想象，使信件合理连贯。 DearAceTravel，   I’m Wang Ming。from the west of China．For the coming winter vacation，my family and I want to spend our vacation in a beautiful place for ten days．We would like to go somewhere not only warm but also interesting．We don’t mind how far we have to go．It has to be a place where we can swim every day, and it would be nice if our hotel is not expensive but clean and comfortable．We like to play no more than$5，000 for the trip．Could you please give us your  suggestions for vacation spots?                                                                      Yours                                                                    Wang Ming Dear Wang Ming，                                                                                                                                                                                                                                        Yours， Gina