因式分解 高分

做呢４題數之前．．．最緊要記得１條式．．．
>>>> a^2 - b^2 = (a-b)(a+b) <<<<

以下４條數o既解法都係一樣...
只需要將o的數變到個樣好似上面條式咁就得架喇 ^^

－－－－－－－－－－－－－－－－－

(A)
　x^2 - 64 y^2
= x^2 - 8^2 * y^2
= x^2 - ( 8y )^2
= ( x - 8y )( x + 8y )

(B)
　a^4 - 1
= ( a^2 )^2 - ( 1 )^2
= ( a^2 - 1 )( a^2 + 1 )

(C)
　5 p^2 - 20 q^2
= 5 ( p^2 - 4 q^2 )
= 5 [ ( p )^2 - ( 2q )^2 ]
= 5 ( p - 2q )( p + 2q )

(D)
　64 - 4m^2
= ( 8 )^2 - ( 2m )^2
= ( 8 - 2m )( 8 + 2m )

2007-08-05 17:35:33 補充：
哈哈...漏左約數o添 =P" sor sor~(D)　64 - 4m^2= 4 ( 16 - m^2 )= 4 ( 4^2 - m^2 )= 4 ( 4 - m )( 4 m )

2007-08-05 17:39:01 補充：
記住呢幾條式會好有用架...要比心機喔 ;]a^2 2ab b^2 = (a b)^2a^2 -2ab b^2 = (a-b)^2a^2 - b^2 = (a-b)(a b)如果條數係a^2 b^2 的話...a^2 b^2= a^2 b^2 2ab - 2ab= ( a b)^2 -2ab 〔OR (a-b)^2 2ab 〕所以...記得呢3條式就計數容易好多架喇=]

2007-08-05 17:39:53 補充：
@@" 冇左o的加號 [ ＋ ] o既...

(A) = (x+8y)(x-8y)

(B= (a^2+1)(a+1)(a-1)

(C)= 5 (p+2q)(p-2q)

(D)= 4 (4-m)(4+m)