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Math Help - L'Hospital for this?

  1. #1
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    L'Hospital for this?

    Very basic question. Van I user L-Hosptial rule there:
    (sorry about lack of latex here)

    when lim x->0 the f(x) 5x^2 / 3x reaches to?
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  2. #2
    Moo
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    Quote Originally Posted by tabularasa View Post
    Very basic question. Van I user L-Hosptial rule there:
    (sorry about lack of latex here)

    when lim x->0 the f(x) 5x^2 / 3x reaches to?
    Hmmm just simplify :
    x^2=x*x

    \implies \frac{5x^2}{3x}=\frac{5 x*x}{3x}=\frac{5x}{3}


    I'm sorry to say, but you'll have to drop this habit of always relying on l'Hospital's rule
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  3. #3
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    Quote Originally Posted by tabularasa View Post
    Very basic question. Van I user L-Hosptial rule there:
    (sorry about lack of latex here)

    when lim x->0 the f(x) 5x^2 / 3x reaches to?
    Yes
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  4. #4
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    Could you give me example for this equation since I try to use L'Hospital I just get:

    using L'H:
    f'(x) / g'(x) = 10x/3

    and L'H again I get:
    10/?
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  5. #5
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    Quote Originally Posted by tabularasa View Post
    Sorry about typo. So I want to use L'Hospital rule in equation above. Is L'Hospital eligible here?
    Yes
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  6. #6
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    Quote Originally Posted by Moo View Post
    Hmmm just simplify :
    x^2=x*x

    \implies \frac{5x^2}{3x}=\frac{5 x*x}{3x}=\frac{5x}{3}


    I'm sorry to say, but you'll have to drop this habit of always relying on l'Hospital's rule
    Heh, so I cant use L'Hospital here? One say Yes and you show me that no it is not usable in this?

    EDIT: Ah, I see, the equation is not in a form where L'Hospital rule works with. Not in 0/0 or infinity/infinity form since 5x^2/3x = 5x/3
    Thanks!
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  7. #7
    Moo
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    Quote Originally Posted by tabularasa View Post
    Heh, so I cant use L'Hospital here? One say Yes and you show me that no it is not usable in this?
    You can use it ! Because both numerator and denominator go to 0..

    But it's not the most suitable method here. If you're not specifically asked to use l'Hospital's rule in this case, then don't. Simplify first.
    Your first question "Can I use" is ambiguous ^^'
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  8. #8
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    Quote Originally Posted by tabularasa View Post
    Heh, so I cant use L'Hospital here? One say Yes and you show me that no it is not usable in this?
    Both ways are correct, notice you get the same answer.
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  9. #9
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    Ok, could you help me on this.

    After use L'H once for 5x^2/3x I will get: 10x/3
    What next?
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  10. #10
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    Quote Originally Posted by tabularasa View Post
    Ok, could you help me on this.

    After use L'H once for 5x^2/3x I will get: 10x/3
    What next?
    Now take the limit x --> 0 (!)
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  11. #11
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    Aargh! It was too obvious. 0/3
    Thanks you guys!
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