5.
某种新产品投放市场一段时间后,经过调研获得了时间\(x(\)天数\()\)与销售单价\(y(\)元\()\)的一组数据,且做了一定的数据处理\((\)如表\()\),并作出了散点图\((\)如图\()\)
\(\overline{x}\) | \(\overline{y}\) | \(\overline{w}\) | \(\sum\limits_{i=1}^{10}{{{({{x}_{i}}-\overline{x})}^{2}}}\) | \(\sum\limits_{i=1}^{10}{{{({{w}_{i}}-\overline{w})}^{2}}}\) | \(\sum\limits_{i=1}^{10}{({{x}_{i}}-\overline{x})({{y}_{i}}-\overline{y})}\) | \(\sum\limits_{i=1}^{10}{({{w}_{i}}-\overline{w})({{y}_{i}}-\overline{y})}\) |
\(1.72\) | \(91.50\) | \(0.83\) | \(5.30\) | \(0.85\) | \(-21.07\) | \(42.50\) |
表中\({{w}_{i}}=\dfrac{1}{{{x}_{i}}}\),\(\overline{w}=\dfrac{1}{10}\sum\limits_{i=1}^{10}{{{w}_{i}}}\).
![](https://www.ebk.net.cn/tikuimages/2/2018/600/shoutiniao48/faab6d1c9481f2cd1b572fa8f9e3a746.png)
\((1)\)根据散点图判断,\(\widehat{y}=\widehat{a}+\widehat{b}x\)与\(\widehat{y}=\widehat{c}+\dfrac{\widehat{d}}{x}\)哪一个更适宜作价格\(y\)关于时间\(x\)的回归方程类型?\((\)不必说明理由\()\)
\((2)\)根据判断结果和表中数据,建立\(y\)关于\(x\)的回归方程;
\((3)\)若该产品的日销售量\(g(x)(\)件\()\)与时间\(x\)的函数关系为\(g(x)=-\dfrac{20}{x}+25(x\in {{N}^{*}})\),求该产品投放市场第几天的销售额最高?最高为多少元?\((\)结果保留整数\()\)
附:对于一组数据\(\left({u}_{1},{v}_{1}\right) \),\(\left({u}_{2},{v}_{2}\right) \),\(\left({u}_{3},{v}_{3}\right) \),\(\cdots \),\(\left({u}_{n},{v}_{n}\right) \),其回归直线\(v=\widehat{\alpha }+\widehat{\beta }u\)的斜率和截距的最小二乘估计分别为\(\widehat{\beta }=\dfrac{\sum\limits_{i=1}^{n}{({{v}_{i}}-\overline{v})({{u}_{i}}-\overline{u})}}{\sum\limits_{i=1}^{n}{{{({{u}_{i}}-\overline{u})}^{2}}}}\),\(\widehat{\alpha }=\overline{v}-\widehat{\beta }\overline{u}\).