about cross-method (20marks)

In Form 2, you will teach factorization.
The methods of factorization usually has several ways to solve it:
- Taking out common factor
- a^2 - b^2 = (a+b)(a-b)
- a^2 + 2ab + b^2 = (a+b)^2
- a^2 - 2ab + b^2 = (a-b)^2
However, if the methods mentioned about cannot solve it.
We will use cross-method.
e.g. Factorize 2x^2 + 5x - 12
2x -3
X
x 4
-----------------
-3x+8x = 5x
2x^2 + 5x – 12 = ( 2x – 3 ) ( x + 4 )



2009-10-07 18:49:29 補充：
*You will be taught.