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liizzyliizz

  • 4 years ago

lim x^3-8/x-2 as x ->2 i know this is easy. but by hand im not getting 12 as the answer. (Something with my factoring i bet) but im tired and i cant think straight help!

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  1. anonymous
    • 4 years ago
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    Use L'Hopital's rule..... Or break x^3-8 as (x-2)(x^2-2x+4)

  2. anonymous
    • 4 years ago
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    factor the numerator as the difference of two cubes and cancel, as notsobright wrote. you probably have not made it to l'hopital yet

  3. anonymous
    • 4 years ago
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    however, that is not how to factor

  4. anonymous
    • 4 years ago
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    no it is \[x^3-8=(x-2)(x^2+2x+4)\]

  5. liizzyliizz
    • 4 years ago
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    Curse my algebra skills ! D:

  6. anonymous
    • 4 years ago
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    plus two, not minus two

  7. anonymous
    • 4 years ago
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    oh sorry its +2x not -2x

  8. anonymous
    • 4 years ago
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    then replace x by 2, get 4+4+4=12

  9. liizzyliizz
    • 4 years ago
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    *cry* lol these small fails will be the death of me.

  10. liizzyliizz
    • 4 years ago
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    I know how to do Limits, but the algebra part was driving me insane O.o

  11. anonymous
    • 4 years ago
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    soon you will be able to do this in your head. you will say "the derivative of \[x^3-8\] is \[3x^2\] and \[3\times 2^2=12\]

  12. anonymous
    • 4 years ago
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    yeah the algebra is always the tricky part, idea is easy part

  13. liizzyliizz
    • 4 years ago
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    yeah I understand the calculus part and the concepts. its the factoring that i mess up in, and those negative signs get to me all the time :(

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