题目
Problem
In this question you must show all stages of your working.
Solutions relying entirely on calculator technology are not acceptable.
A rectangular sports pitch has length x metres and width y metres, where x>y.
Given that the perimeter of the pitch is 350 m,
(a) write down an equation linking x and y.
(1)
Given also that the area of the pitch is 7350 m2,
(b) write down a second equation linking x and y.
(1)
(c) hence find the value of x and the value of y.
(4)
解答
(a)
解法一
思路
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矩形周长是 2x+2y。
答题过程
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2x+2y=350.
(b)
解法一
思路
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矩形面积是长乘宽。
答题过程
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xy=7350.
(c)
解法一
思路
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由周长方程可得 x+y=175,所以 y=175−x。代入面积方程,得到关于 x 的二次方程。最后用 x>y 判断哪个是长度。
答题过程
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From part (a),
x+y=y=175175−x.
Substitute into xy=7350:
x(175−x)=175x−x2=x2−175x+7350=735073500.
Factorise:
(x−70)(x−105)=0.
So
x=70orx=105.
Since x>y,
x=105,y=70.