Indices and Factorising

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  1. IgorYakov's Avatar
    1 11-05-2012  19:10
    • Adored and Respected Member
    • Posts: 471
    Indices and Factorising
    How would you do...

    2^{30} / 8^9

    Also

    A factorising question is: 2x^2-7x+6


    The answer i got was: (2x-6)(x-1)

    The book says: (2x-3)(x-2)

    Could somebody please explain why?
  2. Intriguing Alias's Avatar
    2 11-05-2012  19:13
    • TSR Idol
    • Location: Yorkshire
    Re: Indices and Factorising
    (Original post by IgorYakov)
    How would you do...

    2^{30} / 8^9

    Also

    A factorising question is: 2x^2-7x+6


    The answer i got was: (2x-6)(x-1)

    The book says: (2x-3)(x-2)

    Could somebody please explain why?
    For the first question remember 8 = 2^3

    For the second, multiply your answer out and check to see if you get the original question.
    Post rating:
    1
  3. raheem94's Avatar
    3 11-05-2012  19:13
    • TSR Demigod
    • Posts: 5,512
    Re: Indices and Factorising
    (Original post by IgorYakov)
    How would you do...

    2^{30} / 8^9
    \dfrac{2^{30}}{8^9}

    Remember, 2^3 = 8

    You will need to use the law, (a^b)^c = a^{bc}
  4. zed963's Avatar
    4 11-05-2012  19:14
    • Overlord in Training
    • Posts: 2,134
    Re: Indices and Factorising
    Expand the brackets using the foil method and see where you have gone wrong.
    Post rating:
    1
  5. raheem94's Avatar
    5 11-05-2012  19:15
    • TSR Demigod
    • Posts: 5,512
    Re: Indices and Factorising
    (Original post by IgorYakov)
    A factorising question is: 2x^2-7x+6


    The answer i got was: (2x-6)(x-1)

    The book says: (2x-3)(x-2)

    Could somebody please explain why?
    2x^2-7x+6= 2x^2 - 4x - 3x +6
  6. raheem94's Avatar
    6 11-05-2012  19:20
    • TSR Demigod
    • Posts: 5,512
    Re: Indices and Factorising
    (Original post by hassi94)
    For the first question remember 8 = 2^3

    For the second, multiply your answer out and check to see if you get the original question.
    OP, please don't see the spoiler, you will get confused.

    Spoiler:
    Show

    Can't we expand 2^{30} and divide it by 8^9 \ ?
  7. Intriguing Alias's Avatar
    7 11-05-2012  19:22
    • TSR Idol
    • Location: Yorkshire
    Re: Indices and Factorising
    (Original post by raheem94)
    OP, please don't see the spoiler, you will get confused.

    Spoiler:
    Show

    Can't we expand 2^{30} and divide it by 8^9 \ ?
    Spoiler:
    Show
    Ahahahaha brilliant. This is definitely the best way to do it! :rofl:
  8. raheem94's Avatar
    8 11-05-2012  19:24
    • TSR Demigod
    • Posts: 5,512
    Re: Indices and Factorising
    (Original post by hassi94)
    Spoiler:
    Show
    Ahahahaha brilliant. This is definitely the best way to do it! :rofl:
    Spoiler:
    Show

    Actually the question posted on the thread the other day was exactly the same, see the link: http://www.thestudentroom.co.uk/show...2#post37468612
  9. Intriguing Alias's Avatar
    9 11-05-2012  20:09
    • TSR Idol
    • Location: Yorkshire
    Re: Indices and Factorising
    (Original post by raheem94)
    Spoiler:
    Show

    Actually the question posted on the thread the other day was exactly the same, see the link: http://www.thestudentroom.co.uk/show...2#post37468612
    Yeah I recognised it as soon as I saw it
  10. ThatPerson's Avatar
    10 12-05-2012  00:23
    • Peer Of The TSR Realm
    • Posts: 1,432
    Re: Indices and Factorising
    (Original post by hassi94)
    Yeah I recognised it as soon as I saw it
    Just wondering..

    Spoiler:
    Show
    Is it really worth expanding 2^{30}? In my opinion it's easier to just change the 8^9 into (2^3)^9 and then use the standard law of division.
  11. raheem94's Avatar
    11 12-05-2012  00:26
    • TSR Demigod
    • Posts: 5,512
    Re: Indices and Factorising
    (Original post by ThatPerson)
    Just wondering..

    Spoiler:
    Show
    Is it really worth expanding 2^{30}? In my opinion it's easier to just change the 8^9 into (2^3)^9 and then use the standard law of division.
    Spoiler:
    Show

    We know it!
    Have a look at this link, this question was also posted 2 days ago and someone suggested to expand 2^30.
  12. Intriguing Alias's Avatar
    12 12-05-2012  00:28
    • TSR Idol
    • Location: Yorkshire
    Re: Indices and Factorising
    (Original post by ThatPerson)
    Just wondering..

    Spoiler:
    Show
    Is it really worth expanding 2^{30}? In my opinion it's easier to just change the 8^9 into (2^3)^9 and then use the standard law of division.
    Expanding is a bad idea, we were just kidding around because of a poster who suggested it the other day. The method you stated is by far the best and is what both me and raheem would do.
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