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How to factorise cubic expressions?

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  1. Offline

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    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!!!!
  2. Offline

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    Pull out common factors

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

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

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    (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...
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    (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????
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    (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
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    (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
  8. Offline

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    (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
  9. Offline

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    (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...
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    (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?
  11. Offline

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    (Original post by TenOfThem)
    Then take x out and you have a quadratic to factorise
    Cheers I got it right Your amazing
  12. Offline

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    since everything is in terms of x it's much easier you just pull out x and then factorize the quadratic.
  13. Offline

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    (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
  14. Offline

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    (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.
  15. Offline

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    (Original post by BabyMaths)
    TenOfThem should be getting paid by your school as well as her own.
    LoL
  16. Offline

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    (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...
  17. Offline

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    (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
  18. Offline

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    (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
  19. Offline

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    erm ....

    x^3-x^2 = x^2(x-1)
  20. Offline

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    (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

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