f.4 二元一次方程

(x+1) (x-2) + (x+1)=0
(x + 1)(x - 2 + 1) = 0
(x + 1)(x - 1) = 0
x + 1 = 0 or x - 1 = 0
x = - 1 or x = 1
no need to express .


2009-09-25 18:20:09 補充：
It should be 一元二次方程。

(x+1) (x-2) + (x+1)=0

(x+1) [(x-2) + 1] =0

(x+1) (x-1)=0

(x+1)=0 or (x-1)=0

x=-1 or x=1