Skip to content
CalcGospel 國際數學圖譜
返回

IAL 2023 May Q2

A Level / Edexcel / P1

IAL 2023 May Paper · Question 2

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 xx metres and width yy metres, where x>yx>y.

Given that the perimeter of the pitch is 350350 m,

(a) write down an equation linking xx and yy.

(1)

Given also that the area of the pitch is 73507350 m2^2,

(b) write down a second equation linking xx and yy.

(1)

(c) hence find the value of xx and the value of yy.

(4)

解答

(a)

解法一

思路

展开

矩形周长是 2x+2y2x+2y

答题过程

展开 2x+2y=350.\begin{align*} 2x+2y=350. \end{align*}

(b)

解法一

思路

展开

矩形面积是长乘宽。

答题过程

展开 xy=7350.\begin{align*} xy=7350. \end{align*}

(c)

解法一

思路

展开

由周长方程可得 x+y=175x+y=175,所以 y=175xy=175-x。代入面积方程,得到关于 xx 的二次方程。最后用 x>yx>y 判断哪个是长度。

答题过程

展开

From part (a),

x+y=175y=175x.\begin{align*} x+y=&\,175\\ y=&\,175-x. \end{align*}

Substitute into xy=7350xy=7350:

x(175x)=7350175xx2=7350x2175x+7350=0.\begin{align*} x(175-x)=&\,7350\\ 175x-x^2=&\,7350\\ x^2-175x+7350=&\,0. \end{align*}

Factorise:

(x70)(x105)=0.\begin{align*} (x-70)(x-105)=0. \end{align*}

So

x=70orx=105.\begin{align*} x=70 \quad\text{or}\quad x=105. \end{align*}

Since x>yx>y,

x=105,y=70.\begin{align*} x=105,\qquad y=70. \end{align*}