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Math Help - Finding derivatives

  1. #1
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    Finding derivatives

    Guys, how do I differentiate

    (a) x/7

    and

    (b) (1/4)(√x)

    And finally, what is

    Answer of (a) / Answer of (b)

    Thank You!
    Last edited by mr fantastic; August 18th 2009 at 07:43 AM. Reason: Changed post title
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  2. #2
    Senior Member nikhil's Avatar
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    Lightbulb

    as we know
    d(x^n)/dx nx^(n-1)
    and
    d(ax)/dx = a d(x)/dx where a is a constant

    therefor
    d(x/7)/dx = (1/7) d(x)/dx=1/7 (as d(x)/dx=1)

    you may try other one yourself.feel free to ask if you face any problem.
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  3. #3
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    Quote Originally Posted by nikhil View Post
    as we know
    d(x^n)/dx nx^(n-1)
    and
    d(ax)/dx = a d(x)/dx where a is a constant

    therefor
    d(x/7)/dx = (1/7) d(x)/dx=1/7 (as d(x)/dx=1)

    you may try other one yourself.feel free to ask if you face any problem.

    Am I right in saying that

    a) dy/dx = 1/7

    and

    b) dy/dx = 1 / 8√x

    so my rate of substitution would be (1/7) / (1 / (8√x))/ Is there a way to simplify this further?
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  4. #4
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    Quote Originally Posted by Archimedes View Post
    Am I right in saying that

    a) dy/dx = 1/7 Mr F says: Correct.

    and

    b) dy/dx = 1 / 8√x Mr F says: If you mean dy/dx = 1 /(8√x), then yes you're answer is correct.

    so my rate of substitution would be (1/7) / (1 / (8√x))/ Is there a way to simplify this further? Mr F says: Yes. Note that (a/b) / (c/d) = (ad)/(bc) ...
    ..
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  5. #5
    Senior Member nikhil's Avatar
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    Lightbulb

    well you got the differentiation correct
    now
    simply
    (1/7)/(1/8(x)^(1/2))=(8(x)^(1/2))/7
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  6. #6
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    Ok now Ive got (1 / (8√x)) / 7

    Does that mean my final answer is (8√x)/7 ?

    Edit: Nikhal confirmed in above post.

    Thanks to both of you guys so much!
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  7. #7
    Senior Member nikhil's Avatar
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    Wink

    yes that's the final answer.
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