题目

在数列中，满足，，为的前项和，若，则的值为（ ）A. 126 B. 256 C. 255 D. 254 答案：【答案】D【解析】由题意，数列满足，得到数列为等比数列，由求得数列的首项和公比，利用等比数列的求和公式，即可求解。由题意，数列满足，即，所以数列为等比数列，又由，，即，解得，所以，故选D。17、The old Olympic Games began around the year 776 BC in Greece．Many of the sports  1 the same as they are now．But then women were not  2  to take part in the games．   The first Olympic Games in modem times happened in 1896．They were  3  in Greece，where the games were born．Both the Summer and Winter Olympics are held every four year．The Winter Olympics are usually held two years  4  the Summer Olympics． The 24th Summer Olympics were held in 1988 in Los Angeles（洛杉矶）．The competitors from the People’s Republic of China  5  the games for the first time．The Chinese competitors 6  many medals since then．But most of the medals were won by women．We hope men will 7 their best to win more medals． （    ）1．A．looked            B．had                      C．did                        D．were （    ）2．A．allowed          B．hoped                  C．prepared                D．agreed （    ）3．A．held               B．began                  C．begin                     D．hold （    ）4．A．in front of         B．later                     C．before                    D．earlier （    ）5．A．took part in       B．went to                C．played with            D．joined （    ）6．A．have won         B．are winning            C．had won                 D．won （    ）7．A．work              B．train                    C．compete                 D．do