教我一題因式分解- -+

x^2+x-1 =
x^2 + 2x + 1 + x - 1 - 2x - 1 =
(x - 1)^2 - x - 2 =
(x - 1)^2 - (x + 2) =
(x - 1)^2 - [√(x + 2)]^2 =
[ (x - 1) + √(x + 2) ] [ (x - 1) - √(x + 2) ] =
[ x - 1 + √(x + 2) ] [ (x - 1 - √(x + 2) ]

唔知係咪咁 :
=x(x+1)-1
=(x-1)(x+1)

x^2+x-1 答案應該是...
x(x+1)-1
希望可以幫到你啦!

2006-11-02 13:06:24 補充：
oh... 原來我仲計少左一步! =3='' too bad~