F4 Maths ...
2009-11-22 9:16 pm
Stephen has pruchased a certain number of bicycles. The profit ( $P ) of selling all the bicycles is given by the function P = -r^2 + 480r, where $r is the price of a bicycle. Find the maximum profit.
回答 (1)
2009-11-22 9:23 pm
✔ 最佳答案
P =- r^2 + 480r
= - (r^2 - 480r)
= - (r^2 - 2 * 240 * r )
= - (r^2 - 2 * 240 * r + 240^2 - 240^2)
= - (r^2 - 2 * 240 * r + 240^2) + 240^2
= - (r - 240)^2 + 240^2
when r = 240 ,
The maximum profit P = - (240 - 240)^2 + 240^2
= 240^2 = $57600
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