将等差数列1,4,7,…按一定的规则排成了如图所示的三角形数阵,根据这个排列规则,数阵中第10行最后一个数是_____ .
![](https://img.xkw.com/dksih/QBM/editorImg/2022/10/25/ab2987da-7f32-46c2-8fac-337934940eb3.png?resizew=152)
更新时间:2020-03-16 16:14:01
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【推荐1】将等差数列1,4,7……,按一定的规则排成了如图所示的三角形数阵.根据这个排列规则,数阵中第20行从左至右的第3个数是_______
![](https://img.xkw.com/dksih/QBM/2018/10/15/2054100355350528/null/STEM/4c5b97d699984a2ba2b6512c6bd42f62.png?resizew=155)
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【推荐2】数列
的前
项和为
,若数列
的各项按如下规律排列![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5a6c820f6e2a5ee12d04c70c31f2a7ab.png)
.则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac326f9f4ad78d0053c113f823ea6d60.png)
_______ ;若存在正整数
,使
,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0b3a4c9fb96286846512b1f26e9b33b4.png)
________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5a6c820f6e2a5ee12d04c70c31f2a7ab.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3b57aa646cd5ba1319aa41a64c641679.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac326f9f4ad78d0053c113f823ea6d60.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f0a532e15e232cb4b99a8d4d07c89575.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ef903a3c5bcfe72ce10ac042cfb7322b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0b3a4c9fb96286846512b1f26e9b33b4.png)
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【推荐1】观察下图中各正方形图案,每条边上有
个圆圈,每个图案中圆圈的总数是
,按此规律推出:当
时,
与
的关系式 .
![](https://img.xkw.com/dksih/QBM/2011/4/7/1570107028135936/1570107033018368/STEM/f4ab21f75f5d4d23b85601daa766dcd0.png?resizew=417)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e446b358e506b4585f8495daf1a74ddd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e446b358e506b4585f8495daf1a74ddd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9f613e4dbd9e5a912f928f2bbabc0d42.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0704f453b2de48d36911f7db496bbf82.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://img.xkw.com/dksih/QBM/2011/4/7/1570107028135936/1570107033018368/STEM/f4ab21f75f5d4d23b85601daa766dcd0.png?resizew=417)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e446b358e506b4585f8495daf1a74ddd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e446b358e506b4585f8495daf1a74ddd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d585c6e8a8effb1d854c4a442a80303f.png)
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【推荐2】将全体正整数排成如图的一个三角形数阵,按照此排列规律,第
行从左向右的第
个数为__________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5453184e251cfe787b5965cd38426962.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8b06e95b57b7a81cd81d05557a11fa92.png)
![](https://img.xkw.com/dksih/QBM/2017/11/25/1824938606977024/1826309937209344/STEM/d75071cf2024484ab69bc73118f76dea.png?resizew=189)
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