题目

{an}为等差数列，公差d＞0，Sn是数列{an}前n项和，已知a1a4=27，S4=24． （1）求数列{an}的通项公式an； （2）令bn=an•2n，求数列{bn}的前n项和Tn． 答案：解：（1）∵a1a4=27，S4=24． ∴，解得a1=3，d=2． ∴an=3+2（n-1）=2n+1． （2）bn=an•2n=（2n+1）•2n． ∴数列{bn}的前n项和Tn=3×2+5×22+…+（2n+1）•2n，2Tn=3×22+5×23+…+（2n-1）•2n+（2n+1）•2n+1， ∴-Tn=6+2×（22+23+…+2n）-（2n+1）•2n+1=2+2×-（2n+1）•2n+1=-2+（1-2n）•2n+1， ∴Tn=（2n-1）•2n+1+2．Art of sushi makingBei Restaurant at the Opposite House offers the last sushi preparation class by Max Levy, a New Orleans-born New Yorker, who learned the art of sushi making from masters in Japan. Classes are scheduled at 11:30 am on Dec.2 or 5. Cost is 388 yuan per person, including materials and use of materials.010-6410-5230Festive buffetCBD restaurant at Grand Millennium Beijing offers a festive buffet（自助餐）, featuring roast turkey, until Dec.30. Turkey will be matched with stuffing, cranberry sauce, bread and butter pudding, honey-glazed ham, brandy fruit cakes, and existing gourmet buffet selections.010-6530-9383Christmas dinner partyBeijing Minzu Hotel prepares a dinner party on Christmas Eve. There will be song-and-dance performances, with famous French wines and exciting prizes to win. Cost is 1,680—2,580 yuan per person. 6—10 pm, Dec.24, 1/F, Coffee Mill, Four Seasons Restaurant, 2/F Jin Xiu Palace, and 11/F East Hall and West Hall.010-6601-4466 ext 162Christmas shoppingGet a gift idea at The Peninsula Beijing, where there is a wide range of offerings, or shop in style at The Peninsula Arcade, for fashion, jewelry, leather and other gifts. Or try online shopping at peninsula.com. The Peninsula Boutique is open daily from 11:00am—9:30 pm.010-8516-2888 ext 6691【小题1】Many customers are attracted to Bei Restaurant for its ________.A．brandy fruit cakesB．song-and-dance performancesC．jewelry and leatherD．art of sushi making【小题2】If you want to buy some Christmas gifts for your friends, you’d better go to _________.A．Beijing Minzu HotelB．Grand Millennium BeijingC．The Peninsula BeijingD．Bei Restaurant【小题3】If you are sure to order delicious Turkey by Dec. 30, you can phone _________.  A．010-8516-2888B．010-6601-4466C．010-6530-9383D．010-6410-5230