东汉末年群雄并起,最终形成三国鼎立的格局.下列示意图符合公元222年三国局势的是( )
A:
B:
C:
D:
阅读材料:求值1+2+22+23+24+…+22014
解:设S=1+2+22+23+24+…+22014①,将等式两边同时乘以2得
2S=2+22+23+24+…+22014+22015②
将②﹣①得:S=22015﹣1,即S=1+2+22+23+24+…+22014=22015﹣1
请你仿照此法计算:(1)1+2+22+23+24+…+210
(2)1+3+32+33+34+…+3n(其中n为正整数)
某人沿斜坡坡度i=1:2的斜坡向上前进了6米,则他上升的高度为( )
某班历史兴趣学习小组在自主学习时搜集到以下几幅图片。符合这组图片主题的是( )
阅读短文,掌握大意,然后从A、B、C、D四个选项中,选出可以填入空白处的最佳选项。
A little sports shop is near my house. It sells (卖) many good things for 1 . At the shop, we can buy soccer balls, 2 , basketballs and so on. Today my 3 and I go to the4 to buy a tennis racket. There are a lot of 5 . And they have different 6 . I think every racket 7 very nice. My sister chooses (选择) a black one, because black is her favorite8 . You know, my sister is a big sports fan. She has a great sports 9 at home-five soccer balls, four basketballs and many tennis balls. She really likes 10 sports.