Results are out! Find what you need...fast. Get quick advice or join the chat
Hey! Sign in to get help with your study questionsNew here? Join for free to post

How to factorise cubic expressions?

Announcements Posted on
Applying to Uni? Let Universities come to you. Click here to get your perfect place 20-10-2014
    • Thread Starter
    • 39 followers
    Offline

    ReputationRep:
    Ok so y = x^3 + x^2 - 2x

    How do I do this

    And x^3 - x^2

    and x^3 = 9x


    Basically I've used these questions because each one is different and uses different techniques

    Thanks!!!!
    • 229 followers
    Online

    ReputationRep:
    Pull out common factors

    Posted from the Bottom of the Big Blue Sea...
    • 0 followers
    Offline

    ReputationRep:
    Have you done remainder theorem? I.e.  f(x) =x^3 + x^2 -2x , when f(y)=0, (x-y) is a factor.
    • 229 followers
    Online

    ReputationRep:
    (Original post by Atheism)
    Have you done remainder theorem? I.e.  f(x) =x^3 + x^2 -2x , when f(y)=0, (x-y) is a factor.
    Thats the factor theorem

    Posted from the Bottom of the Big Blue Sea...
    • Thread Starter
    • 39 followers
    Offline

    ReputationRep:
    (Original post by shadab786ahmed)
    Pull out common factors

    Posted from the Bottom of the Big Blue Sea...

    (Original post by Atheism)
    Have you done remainder theorem? I.e.  f(x) =x^3 + x^2 -2x , when f(y)=0, (x-y) is a factor.

    (Original post by shadab786ahmed)
    Thats the factor theorem

    Posted from the Bottom of the Big Blue Sea...
    No I haven't
    only x is a common factor????
    • 66 followers
    Offline

    ReputationRep:
    (Original post by shadab786ahmed)
    Thats the factor theorem

    Posted from the Bottom of the Big Blue Sea...
    Sure, but the factor theorem is only a special case of the remainder theorem so it is the remainder theorem
    • 66 followers
    Offline

    ReputationRep:
    (Original post by Blueray2)
    No I haven't
    only x is a common factor????
    Then take x out and you have a quadratic to factorise
    • Thread Starter
    • 39 followers
    Offline

    ReputationRep:
    (Original post by TenOfThem)
    Then take x out and you have a quadratic to factorise
    oh so x(x^2+x-2)

    then I solve x^2+x-2=0
    to get 2 x brackets

    and the first x is just = 0
    • 229 followers
    Online

    ReputationRep:
    (Original post by TenOfThem)
    Sure, but the factor theorem is only a special case of the remainder theorem so it is the remainder theorem
    That makes sense

    Posted from the Bottom of the Big Blue Sea...
    • 66 followers
    Offline

    ReputationRep:
    (Original post by Blueray2)
    oh so x(x^2+x-2)

    then I solve x^2+x-2=0
    to get 2 x brackets

    and the first x is just = 0
    yes

    remind me ... do you go to school and have a teacher or is this all you?
    • Thread Starter
    • 39 followers
    Offline

    ReputationRep:
    (Original post by TenOfThem)
    Then take x out and you have a quadratic to factorise
    Cheers I got it right Your amazing
    • 6 followers
    Offline

    ReputationRep:
    since everything is in terms of x it's much easier you just pull out x and then factorize the quadratic.
    • Thread Starter
    • 39 followers
    Offline

    ReputationRep:
    (Original post by TenOfThem)
    yes

    remind me ... do you go to school and have a teacher or is this all you?
    I go school, but the teacher doesn't help, he refuses to, and I get loads of H.w
    but it's fine I got it right with your help
    • 8 followers
    Offline

    ReputationRep:
    (Original post by Blueray2)
    I go school, but the teacher doesn't help, he refuses to, and I get loads of H.w
    but it's fine I got it right with your help
    TenOfThem should be getting paid by your school as well as her own.
    • 66 followers
    Offline

    ReputationRep:
    (Original post by BabyMaths)
    TenOfThem should be getting paid by your school as well as her own.
    LoL
    • 229 followers
    Online

    ReputationRep:
    (Original post by TenOfThem)
    x
    :eek: sorry! Didn't realise you were female I am on the app so cant see the signs!

    Posted from the Bottom of the Big Blue Sea...
    • Thread Starter
    • 39 followers
    Offline

    ReputationRep:
    (Original post by BabyMaths)
    TenOfThem should be getting paid by your school as well as her own.
    :lol: I swear one day when I'm rich i'll make my own school which gives free tutoring
    • Thread Starter
    • 39 followers
    Offline

    ReputationRep:
    (Original post by BabyMaths)
    TenOfThem should be getting paid by your school as well as her own.

    (Original post by TenOfThem)
    LoL

    (Original post by shadab786ahmed)
    :eek: sorry! Didn't realise you were female I am on the app so cant see the signs!

    Posted from the Bottom of the Big Blue Sea...
    For the 2nd one I got
    x^3 - x^2

    = x(x^2-x)

    what does (x^2-x) =
    I mean in terms of x values to draw the sketchs
    • 66 followers
    Offline

    ReputationRep:
    erm ....

    x^3-x^2 = x^2(x-1)
    • Thread Starter
    • 39 followers
    Offline

    ReputationRep:
    (Original post by TenOfThem)
    erm ....

    x^3-x^2 = x^2(x-1)
    lol yh my bad, was abt to edit that

    Ok so x^2 = (x)(x)
    so x = 0
    and x =1
    thanks I get it

Reply

Submit reply

Register

Thanks for posting! You just need to create an account in order to submit the post
  1. this can't be left blank
    that username has been taken, please choose another Forgotten your password?
  2. this can't be left blank
    this email is already registered. Forgotten your password?
  3. this can't be left blank

    6 characters or longer with both numbers and letters is safer

  4. this can't be left empty
    your full birthday is required
  1. By joining you agree to our Ts and Cs, privacy policy and site rules

  2. Slide to join now Processing…

Updated: September 26, 2012
New on TSR

Personal statement help

Use our clever tool to create a PS you're proud of.

Article updates
Reputation gems:
You get these gems as you gain rep from other members for making good contributions and giving helpful advice.