Factorization by cross method

Zidane

2009-12-19 3:23 am

I know we can factorize by using cross method, but how?

I am very familiar with other methods, and other things which are taught in form first term, but my teacher hasn't taught me about cross method, can someone teach me and give me some example?

回答 (1)

[匿名]

2009-12-19 4:39 am

✔ 最佳答案

for example

2x^2 + 7x + 6

by cross method

2ｘ　　３
　＼／
　／＼
ｘ　　２

左手邊2ｘ* ｘ　=2x^2
右手邊2*3=6

上面個2x *2=4x
下面個x *3=3x
加埋= 7x

加埋曬就係 2x^2 + 7x + 6
Factorize 就係
(2x+3)(x+2) (橫向寫出來)

再比多個 example

3x^2 -11x -4

3x　　1
　＼／
　／＼
x　　-4
左手邊3ｘ* ｘ　=3x^2
右手邊-4*1=-4

上面個3x * -4= -12x
下面個x *1=x
加埋= -11x

加埋曬就係3x^2 -11x -4
Factorize 就係
(3x+1)(x-4) (橫向寫出來)

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