數學(簡單)！

2/(a-1) + 1/(1-x)
令到分母相同先..
左面個數就(1-x)/(1-x)...因為(1-x)/(1-x)=1..所以數值無變..
右面就用番差唔多方法..之後大家分母一樣就可以分子相加..

2(1-x)/(a-1)(1-x) + 1(a-1)/(a-1)(1-x)

=(2-2x+a-1)/(a-1)(1-x)

=(1-2x+a)/(a-1)(1-x)//

2007-08-10 16:18:00 補充：
含有變數的字母....即係有未知數...a,b,c,d.......z都算係..呢條式有變數的分母有2個:a同x

2(1-x)/(a-1)(1-x) + 1(a-1)/(a-1)(1-x)

=(2-2x+a-1)/(a-1)(1-x)

=(1-2x+a)/(a-1)(1-x)//

通分母@@

2(1-X)+a-1
______________
(a-1) (1-X)

=1-2x+a
_________
(a-1) (1-X)

3
一一一一一
1-x+1-a
3
=一一一一
2-x-a
去到lay度已經冇得計,因為你唔知嗰兩個未知數係乜.

令到分母相同先..
左面個數就(1-x)/(1-x)...因為(1-x)/(1-x)=1..所以數值無變..
右面就用番差唔多方法..之後大家分母一樣就可以分子相加..

2(1-X)+a-1
______________
(a-1) (1-X)

=1-2x+a
_________
(a-1) (1-X)

通分母和進行加減, 把它化到最簡

2/a-1 + 1/1-x
=2-2x+a-1
=1-2x+a