Factorization And Mensuration

Factorize the following expressions
1.(x+y)(2x-y)-3x-3y
= (x+y)(2x-y) - 3(x+y)
= (x+y)(2x-y - 3)

2.(x+y)(2a-3b)+(x+y)(2b-c)
= (x+y)(2a-3b + 2b-c)
= (x + y)(2a - b - c)
Conventional Question
1.A sector has radius 10cm and area 40兀 平方厘米.Find the perimeter of the sector.

= 2 radius + arc
= 2(10) + 2π(10) * 40π / [π(10)^2]
= 20 + 20π * 2/5
= 20 + 8π
= 4(2π + 5) cm
or
= 45.13(2 dec.) cm



2.A sector of radius 6cm has perimeter 20cm.Find,correct to the nearest degree, the angle of the sector.
Let x be the angle :
(20 - 6*2) = 2π(6) * x/360
8 = 0.10472 x
x = 76.39437
The required angle = 76° (nearest degree)

(x+y)(2x-y)-3x-3y
(x+y)(2x-y)-3(x+y)
(x+y)(2x-y-3)


(x+y)(2a-3b)+(x+y)(2b-c)
(x+y)(2a-3b+2b-c)
(x+y)(2a-b-c)


(theta/360)x10^2pi=40pi
theta /360 =2/5
theta =144o

2pi(10)x(144/360)
=8pi cm

2010-06-22 22:28:29 補充：
8pi+20

2010-06-22 22:40:02 補充：
A sector of radius 6cm has perimeter 20cm.Find,correct to the nearest degree, the angle of the sector.

2(pi)(6)x(theta/360)+12=20
12pi(theta)/360 =8
theta =76.3