解题方法
1 . 已知有穷数列
、
(
),函数
.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/5/6/94f52bd7-eb80-462e-b83f-122a7931d7a7.png?resizew=187)
(1)如果
是常数列,
,
,
,在直角坐标系中在画出函数
的图象,据此写出该函数的单调区间和最小值,无需证明;
(2)当
,
(
)时,判断函数
在区间
上的单调性,并说明理由;
(3)当
,
,
时,求该函数的最小值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63d471926f7b27322d90c82b9ce21d3d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5fce83115a50f99e08e9a2db7267aeed.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dd3b7a416df75d4f8670214153b9f5d4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/af44b29c584de1e16bb6f46a8d1b6c75.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/5/6/94f52bd7-eb80-462e-b83f-122a7931d7a7.png?resizew=187)
(1)如果
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63d471926f7b27322d90c82b9ce21d3d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e15ffa7fecea3704dc892ea8cd513c59.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/44a8100f98999e472945ab7050af50d3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/367e788c32187ae2cc97aaa24da1d40d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4fe7d5809da02c15a43a0e9a898b9086.png)
(2)当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/05d9e81193c41bc99745568cf8c08f56.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f6f812698a6f8b1e0041b1e08159a3d4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a899d786e1c9ca96e401f07bea4e55b1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4fe7d5809da02c15a43a0e9a898b9086.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c512846522aa513bd39f4b320ca68506.png)
(3)当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b80c1ed7b10ac7ca1cd81cdd39a8fcc0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3393ba5ecb4e38bdcde190c8ffcaca92.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dc7c9137c7f1f0ce38a3b0cfd6d28696.png)
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