这道题怎么做?A rectangle is inscribed with its base on the x axis

来源：学生作业帮编辑：作业帮分类：数学作业时间：2024/05/21 16:42:58

这道题怎么做?
A rectangle is inscribed with its base on the x axis and its upper comers on the parabola y=5-x^2. What are the dimensions of such a rectangle with the greatest possible area?
想问一下是可以变成求S（y）=2y乘根号下(5-y)的最大值吗 ?==>或者说求S^2=20y^2-4y^3的最大值?

upper comer是指的矩形的两个上定点吗?
如果是的话就很简单了
建系,设坐标,求导.
设右上定点为（x,5-x^2）(0
再问：不用导数呢..?
再答：求S（y）=2y乘根号下(5-y)的最大值,求S^2=20y^2-4y^3的最大值,这两个都是可以的，但是不用导数我也不会求，你就用导数呗。不过如果用导数的话，最好用我的设法求导，因为求S（y）=2y乘根号下(5-y)的最大值涉及对根号求导，容易出错，求S^2=20y^2-4y^3的最大值求完了容易忘记开平方。

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