three sides of a retangular playground are to be surrounded by a 60m
fence,,the remaining side is the entrance of the playground
a...find the maximum arrea of the playground
b...find the dimensions of the retangular playground if its area is a maximum
THZ
好緊急..
2007-10-16 7:52 am
回答 (1)
2007-10-16 8:04 am
✔ 最佳答案
(a) Let x be length of 1 side. Then (60-2x) is the length of another side.Area
= x(60-2x)
= 60x - 2x^2
= -2(x^2 - 30x + 15^2) + 2(15^2)
= -2(x - 15)^2 + 450
Therefore, the maximum area is 450m^2
(b) When the area is maximum, x = 15
Then the other side is 60 - 2x = 60 - 2(15) = 30
Therefore the dimension is 30m x 15m.
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