F.2 Factorization !!

(x-3)²-4x²
(x-3)²-(2x)²
=[(x-3)+2x][(x-3)-2x]
=(3x-3)(-x-3)
=-3(x-1)(x+3)

2006-11-25 17:55:06 補充：
a²-b²=(a+b)(a-b)

因為(a+b)(a-b)
=a²-b²



所以(x-3)²-4x²
=[(x-3)+2x][(x-3)-2x]
=(3x-3)(-x-3)
=3(x-1)(-x-3)
=-3(x-1)(x+3)

(x-3)²-4x²

=(x-3)²-(2x)²
=[(x-3)+2x][(x-3)-2x]
=(x-3+2x)(x+3-2x)
=(3x-3)(-x+3)
=-(3x+3)(x-3)
=-3(x+3)(x-3)
=-3(x-3)²

(x-3)²-4x²

solution
= x² - 3² - 6x - 4x²
= -9 - 6x - 3x² //








(錯唔關我事)

(x-3)² - 4x²
=(x-3)²-(2x)²
= [(x-3)+(2x)] * [(x-3)-(2x)]
= (3x-3) (-3-x)
= - (3x-3) (3+x)
= - 3 (x-1)(3+x)

Reason:
x² - y²
=(x+y)(x-y)

2006-11-25 17:56:51 補充：
factorization 係得一個term咋，上面果個錯左

(x-3)²-4x²
=(x-3)²-(2x)²
=(x-3-2x)(x-3+2x)
=(x-3)(3x-3)

(x-3)²-4x²
=(x²-6x+9)-4x²
=-3x²-6x+9
=-3(x²+2x-3)
=-3(x+3)(x-1)

2006-11-25 17:53:17 補充：
上面2條友唔記得抽3出來係錯

(x-3)²-4x²
= [(x-3)+2x][(x-3)-2x]
= (x-3+2x)(x-3-2x)
= (3x-3)(-x-3)
= -(x+3)(3x-3)

2006-11-25 17:53:16 補充：
= -3(x+3)(x-1)