一條中4 畫圖計數題,,,急問

[匿名]

2008-08-26 12:30 am

a farmer is planning yo surround a rectangular field beside a river with a
fence.the ratio of the length of the field to its width should not be less than3:2 and shouldnot be greater than 2:1,the preimeter of the field should not be less than 30M and should not be greater than60M,let the length and the width of the field be X M and YM respectively

要畫一個graph 黎計數,,,,我想知道所以條件先可以畫
條件例如: x>0 y>0 果d 等等

回答 (1)

比分快!開心哂

2008-08-26 1:38 am

✔ 最佳答案

let length be L and Width be W
i.e. L=XM and W=YM or simply X and Y, omit the meter here 1st
the ratio of the length of the field to its width should not be less than3:2
length : width = X/Y >= 3/2, i.e. 2X>=3Y, 2X-3Y>=0--------( 1 )
the ratio of the length of the field to its width should not be greater than 2:1
length : width = X/Y <=2/1, i.e. X<=2Y, X-2Y<=0------------( 2)
the preimeter of the field should not be less than 30M
30<=2xlength+2xwidth, i.e. 30<=2X+2Y, 15<=X+Y----------( 3 )
the preimeter of the field should not be greater than60M
2xlength+2xwidth<=60, i.e. 2X+2Y<=60, X+Y<=30----------( 4 )
since fence cannot be negative and zero,
then X>0 ---------------------------------------------------------------( 5 )
and Y>0 ----------------------------------------------------------------( 6 )

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