f.4 amathz,,,solving equation with absolute value.

As follows~

圖片參考：http://i248.photobucket.com/albums/gg191/ncy_0916/maths208.jpg?t=1224508088


2008-10-22 17:15:37 補充：
你都可以將佢柝成 (x-3)(x+3)

│x+3│=│x^2-9│
│x+3│=│x+3││x- 3│
│x+3││x- 3│-│x+3│= 0
│x+3│(│x- 3│- 1) = 0
x + 3 = 0 or │x - 3│= 1 or -1
x = -3 or x = 2 or 4

method 3:

│x+3│=│x^2-9│
│x+3│=│(x+3)(x-3)│
│x+3│=│(x+3)││(x-3)│
│(x+3)││(x-3)│- │x+3│= 0
│x+3│(│(x-3)│- 1) = 0
│x+3│= 0 or │(x-3)│= 1
x = -3 or x-3 = 1 or x-3 = -1
x = -3 or x = 4 or x = 2