點樣分解呢條因式「2x^2-32」?

首先要知道一條formula:
x^2 - b^2 = (a+b)(a-b)

so
2x^2 - 32
= 2x^2 - 2(16)
= 2( x^2 - 16)
= 2(x^2 - 4^2)

let a = x, b = 4
then,

= 2(x-4)(x+4) <----answer

2x^2 - 32

= 2(x^2 - 16)

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

=2(x^2-16)
冇步驟可言，可直接去答案！

2007-09-09 01:12:12 補充：
sor, 漏了幾步......2x^2-32=2(x^2-16)=2(x^2-4^2)=2(x 4)(x-4)

2x^2 - 32
= 2(x^2 - 16)
= 2(x^2 - 4^2)
= 2(x - 4)(x + 4)