# Quod Erat Demonstrandum

## 2011/03/18

### 某兩題中四數

Filed under: NSS — johnmayhk @ 5:02 下午

1.

A wire of 80 cm long is cut into two pieces and each wire is bent into a square.
The length of each side of the smaller square is $x$ cm.

(a) Express the total area of the two squares in terms of $x$.
(b) Find the minimum area of the two squares in total.

(a) $(2x^2-40x+400)$ $cm^2$
(b) 200 $cm^2$

2.

A rectanglar lawn with a length of $x$ m and a width $y$ m is to be planted with flowers. The relevent information of the lawn is as follows.

I. The perimeter of the lawn should be between 20 m and 46 m inclusive.

II. The length of the lawn should be greater than the width, but not greater than 5 times the width.

Write down all the constraints.

$10 \le x+y\le 23$
$y
$x>0$
$y>0$

$10 \le x+y\le 23$
$y

## 1 則迴響 »

1. 寧願寫多, 不要寫少

迴響 由 roviury fung — 2011/03/27 @ 12:49 下午 | 回應