Please I need to know how to factorise this quadratic expression!

Please solve it for me and show me the correct and right method to solving these kind of questions.

(xcubed + 2xsquared - 5x - 6)

Please help

and Thanks alot :)

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- Feb 7th 2009, 03:03 AMitsMoeyyFactorising - Please Help!
Please I need to know how to factorise this quadratic expression!

Please solve it for me and show me the correct and right method to solving these kind of questions.

(xcubed + 2xsquared - 5x - 6)

Please help

and Thanks alot :) - Feb 7th 2009, 03:17 AMmathaddictRe :

$\displaystyle P(x)=x^3+2x^2-5x-6$

Well , are you familiar with the factor theorem ?

If not , note that for a polynomial P(x),(x-a) is a factor of P(x) if and only if P(a)=0 .

Notice that the constant term for the equation above is -6 .

Hence if (x-a) were to be a factor of P(x) , then a must be a factor of -6.

a=+/-1,+/-2,+/-3,+/-6

Substitute :

If x=1 , P(1)=1+2-5-6=-8 , hence (x-1) is NOT a factor .

If x=-1,P(-1)=-1+2+5-6=0 , hence (x+1) IS a factor .

Try doing this for all values of a stated above and you should get all the factors for this equation . - Feb 7th 2009, 03:51 AMitsMoeyy
Wow..

Thanks alot.. Your a genius! :D

But I have no idea how to do it..

Could you explain it a bit more?

and could you also solve the question? (Worried)

Im kind of dumb so yeahh.. =/ - Feb 7th 2009, 04:04 AMADARSH
$\displaystyle

1 ------x^3+2x^2-5x-6)

$

$\displaystyle

2-----x^3+x^2+x^2+x-6x-6

$

$\displaystyle

3------x^2*(x+1)+x*(x+1)-6*(x+1)

$

$\displaystyle

4------(x^2+x-6)*(x+1)

$

$\displaystyle

5------(x^2+3x-2x-6)*(x+1)

$

$\displaystyle

6------(x*(x+3)-2*(x+3))*(x+1)

$

$\displaystyle

7------(x-2)*(x+3)*(x+1)

$(Nod) - Feb 7th 2009, 04:06 AMitsMoeyy
HOLY MOLEY!

Niceee

How did ya do that? o.O - Feb 7th 2009, 04:07 AMmathaddict
- Feb 7th 2009, 05:04 AMADARSH
I have edited my post tell the step where you didn't get it

Note: * stands for multiplication