MATHS QUESTIONS FORM2

[匿名]

2007-08-09 12:36 am

q.1 in the figure , five similar retangles are drawn.
pic: http://pichost.xzmo.com/view.php?p=20070808161555.JPG

(a)find the areas of rectanle A and rectangle B.
(b)find the total area of the five rectangles.

q.2 expand -2 (3k-5)(5-3k).

回答 (1)

用戶82723

2007-08-09 12:46 am

✔ 最佳答案

(a) Area of rectangle A
= (x + 2)(x + 5)
= x^2 + 7x + 10

Since the five rectangles are similar,
Area of rectangle B: Area of rectangle A = (2x + 4)^2 : (x + 2)^2 = 4 : 1
So area of rectangle B = 4x^2 + 28x + 40

(b) Similar to (a), area of rectangle C = 9 x Area of rectangle A
Area of rectangle D = 16 x Area of rectangle A
Area of rectangle E = 25 x Area of rectangle A

So the total area of the rectangles
= (1 + 4 + 9 + 16 + 25)(x^2 + 7x + 10)
=55x^2 + 385x + 550

2. -2 (3k-5)(5-3k)
= -2 (3k-5) [ -(3k - 5)]
= 2(3k - 5)^2
= 2(9k^2 - 30k + 25)
= 18k^2 - 60k + 50

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