当n=1时，a1=S1=7；
当n≥2时，an=Sn﹣Sn﹣1=n2+n+5﹣（n﹣1）2+（n﹣1）+5=2n．
∵a1=7不适合上式．an= {#mathm
A: Hello, Kate. ____
B: That's beautiful. I like it.
A: ____
B: I need four.
B: They're funny.
A: You can also buy a T-shirt for your friend.
B: ____
A. Good idea.
B. What about these caps?
C. Come and look at this cap.
D. How many caps do you need?
E. Let's go.
已知向量a→与b→不平行，且|a→|=|b→|≠0，则下列结论中正确的是（ ）
根据汉语提示完成句子。（1）我们在水族馆照了几张像．We____ some ____ at the aquarium．非常感谢你送给我这么精美的礼物。Thank you very much for____me ____ beautiful gift昨天下了一整天雨。It____yesterday．前天没人去动物园，因为天气太糟糕了。No one ____ the ZOO because the weather____too bad．我们今天下午开车去兜风吧。Let's____ this afternoon．
