Results 1 to 7 of 7

Math Help - Factorising - Please Help!

  1. #1
    Newbie
    Joined
    Feb 2009
    Posts
    16

    Exclamation Factorising - 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
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Sep 2008
    From
    West Malaysia
    Posts
    1,261

    Re :

    Quote Originally Posted by itsMoeyy View Post
    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

    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 .
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Feb 2009
    Posts
    16
    Wow..

    Thanks alot.. Your a genius!

    But I have no idea how to do it..

    Could you explain it a bit more?

    and could you also solve the question?

    Im kind of dumb so yeahh.. =/
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Like a stone-audioslave ADARSH's Avatar
    Joined
    Aug 2008
    From
    India
    Posts
    726
    Thanks
    2
    Quote Originally Posted by itsMoeyy View Post
    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
     <br />
1 ------x^3+2x^2-5x-6)  <br />
     <br />
2-----x^3+x^2+x^2+x-6x-6<br />
     <br />
3------x^2*(x+1)+x*(x+1)-6*(x+1)<br />
     <br />
4------(x^2+x-6)*(x+1)<br />
     <br />
5------(x^2+3x-2x-6)*(x+1)<br />
     <br />
6------(x*(x+3)-2*(x+3))*(x+1)<br />
     <br />
7------(x-2)*(x+3)*(x+1)<br />
    Last edited by ADARSH; February 7th 2009 at 06:03 AM. Reason: reply
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    Feb 2009
    Posts
    16
    HOLY MOLEY!

    Niceee

    How did ya do that? o.O
    Last edited by mr fantastic; February 7th 2009 at 05:09 AM. Reason: Replaced a word
    Follow Math Help Forum on Facebook and Google+

  6. #6
    MHF Contributor
    Joined
    Sep 2008
    From
    West Malaysia
    Posts
    1,261
    Quote Originally Posted by itsMoeyy View Post
    Wow..

    Thanks alot.. Your a genius!

    But I have no idea how to do it..

    Could you explain it a bit more?

    and could you also solve the question?

    Im kind of dumb so yeahh.. =/

    Erm , i have probably explained everything or perhaps i am missing something ..

    but i think it is better if you post your working ( substitute all the a's like what i did ) or i do not know where else i can explain
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Like a stone-audioslave ADARSH's Avatar
    Joined
    Aug 2008
    From
    India
    Posts
    726
    Thanks
    2
    I have edited my post tell the step where you didn't get it
    Note: * stands for multiplication
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. factorising x^2 - x + 4
    Posted in the Algebra Forum
    Replies: 2
    Last Post: December 17th 2011, 05:23 AM
  2. Help with factorising
    Posted in the Algebra Forum
    Replies: 2
    Last Post: June 10th 2009, 01:35 PM
  3. Factorising 2
    Posted in the Algebra Forum
    Replies: 2
    Last Post: April 11th 2009, 07:28 AM
  4. factorising
    Posted in the Algebra Forum
    Replies: 1
    Last Post: February 27th 2009, 11:03 AM
  5. Factorising .
    Posted in the Math Topics Forum
    Replies: 2
    Last Post: February 15th 2009, 07:00 AM

Search Tags


/mathhelpforum @mathhelpforum