Factorization一條!!!

2s^2-9t^2-3st
= (2s+3t)(s-3t)

註解:通常factorize的時候..係會攞有index的數尼睇..
見到2s^2的時候, 都係好容易咁寫成(2s)(s)
之後..佢就會變左一條咁的數: (2s??)(s??)
由於-9t^2係negative number..所以佢一定要係等於一個positive number times 一個negative number= e.g.(3t)(-3t)/-t(9t)/-9t(t)
咁之後你就只可以慢慢試...

p.s.其實有個快啲的方法..F.3會教

WHY 001答案錯???

2s2-3st-9t2等於(2s+3t)(s-3t)係用左十字相乘法作因式分解~

2s2-9t2-3st
=2s2-3st-9t2
=(2s+3t)(s-3t)

2009-04-14 13:33:26 補充：
但答案跟001一樣。
應該沒有錯~

2009-04-15 22:50:03 補充：
利用十字相乘法可得
2s^2-3st-9t^2=(2s+3t)(s-3t)

2s^2-9t^2-3st

= 2s^2-3st-9t^2
= (-3t+s)(3t+2s)

2009-04-14 12:19:49 補充：
把 2s^2 拆做 2s , s
把 -9t^2 拆做 -3t , 3t
(-3t)(2s)+(3t)s = -3st
so, = (-3t+s)(3t+2s)

2009-04-14 14:45:47 補充：
吓???
答案呢?

2009-04-14 18:50:24 補充：
haha
唔通(-3t+s)(3t+2s) 唔等於(2s+3t)(s-3t)????
funny~~

2009-04-14 22:54:34 補充：
其實諗下都好有趣
一批高學歷的人 要被發問者選擇誰的答案是正確~~
哈哈~~

2009-04-14 22:58:09 補充：
lwpawanui
in fact i don't understand your explaination.....
may you teach me any faster way to do factorization
i am not statisfy my method either......