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Math Help - How to find the derivative of this function

  1. #1
    Junior Member ImaCowOK's Avatar
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    How to find the derivative of this function

    y = 6e^x

    Does the Power Rule apply? Or does e^x stay the same? I tried with the Power Rule and it got confusing and messy.
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  2. #2
    Senior Member yeKciM's Avatar
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    Quote Originally Posted by ImaCowOK View Post
    y = 6e^x

    Does the Power Rule apply? Or does e^x stay the same? I tried with the Power Rule and it got confusing and messy.
     (6e^x)' = 6e^x

    because when doing derivation you are doing derivation only of functions with "x" can do it by chain rule

     (6e^x)' = 6' \cdot e^x + 6\cdot (e^x)' = 0\cdot e^x + 6 \cdot e^x = 6e^x
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  3. #3
    Junior Member ImaCowOK's Avatar
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    We haven't learned the chain rule, is there another way? If not, I'll just learn the chain rule.
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  4. #4
    Senior Member yeKciM's Avatar
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    Quote Originally Posted by ImaCowOK View Post
    We haven't learned the chain rule, is there another way? If not, I'll just learn the chain rule.
    you can look at it like this ...

     (6e^x)' = 6(e^x)' = 6e^x

    because you pull out the constant ... and now you just do derivation of the function with x
    Last edited by yeKciM; September 10th 2010 at 02:08 PM.
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  5. #5
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    Quote Originally Posted by ImaCowOK View Post
    y = 6e^x

    Does the Power Rule apply? Or does e^x stay the same? I tried with the Power Rule and it got confusing and messy.
    All you need are two things:

    1. The derivative of e^x is e^x. (If you have not learned this then there is no point attempting questions that require knowing it).

    2. If y = a f(x) then dy/dx = a f'(x).
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  6. #6
    Junior Member ImaCowOK's Avatar
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    Quote Originally Posted by mr fantastic View Post

    If you have not learned this then there is no point attempting questions that require knowing it
    Yep, that pretty much explains my class - homework problems on stuff we haven't been taught.
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  7. #7
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    Quote Originally Posted by ImaCowOK View Post
    Yep, that pretty much explains my class - homework problems on stuff we haven't been taught.
    But surely you have a textbook or lecture notes.
    Use them. Look up the topic even if you have not seen it in class.
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  8. #8
    Junior Member Revy's Avatar
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    Quote Originally Posted by yeKciM View Post
     (6e^x)' = 6' \cdot e^x + 6\cdot (e^x)' = 0\cdot e^x + 6 \cdot e^x = 6e^x
     (6e^x)' = 6' \cdot e^x + 6\cdot (e^x)' = 0\cdot e^x + 6 \cdot (x)'e^x = 6e^x
    in case x=-x answer would change to -6e^{-x}
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  9. #9
    Senior Member yeKciM's Avatar
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    Quote Originally Posted by Revy View Post
     (6e^x)' = 6' \cdot e^x + 6\cdot (e^x)' = 0\cdot e^x + 6 \cdot (x)'e^x = 6e^x
    in case x=-x answer would change to -6e^{-x}
    you should probably do :

    \displaystyle  (Ae^{ax})' = ?

    \displaystyle  (Ae^{-ax})' = ?

    \displaystyle  (x^Ae^{ax})' = ?

    \displaystyle  (A^xe^{ax})' = ?




    Quote Originally Posted by mr fantastic View Post
    Given the obvious background of the OP, the previous two replies are less than helpful. Post #5 is all that is required for the OP to understand at this point in time. Product rules etc. are not appropriate for this thread as it will just confuse the OP.
    sorry about that ... del this post (#9) please
    Last edited by yeKciM; September 10th 2010 at 03:19 PM.
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  10. #10
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    Given the obvious background of the OP, the previous two replies are less than helpful. Post #5 is all that is required for the OP to understand at this point in time. Product rules etc. are not appropriate for this thread as it will just confuse the OP.
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  11. #11
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    Quote Originally Posted by ImaCowOK View Post
    Yep, that pretty much explains my class - homework problems on stuff we haven't been taught.
    If that is true, then your problem is with the teacher and I would suggest that you discuss the matter with him/her.
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  12. #12
    Junior Member ImaCowOK's Avatar
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    Quote Originally Posted by Plato View Post
    But surely you have a textbook or lecture notes.
    Use them. Look up the topic even if you have not seen it in class.
    Quote Originally Posted by mr fantastic View Post
    If that is true, then your problem is with the teacher and I would suggest that you discuss the matter with him/her.
    I do use the textbook as well as my notes. It's not as easy as that for someone who has never studied calculus before. I came here for help, not for a scolding. Is this not called "Math Help Forum"? If I have the wrong impression of what this site is for and my presence is bugging other users just say so and I'll leave. There's no need to be so insulting when you know nothing about the situation mr fantastic.

    I've gotten all that I needed from this thread. Thanks.
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  13. #13
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    Quote Originally Posted by ImaCowOK View Post
    I do use the textbook as well as my notes. It's not as easy as that for someone who has never studied calculus before. I came here for help, not for a scolding. Is this not called "Math Help Forum"? If I have the wrong impression of what this site is for and my presence is bugging other users just say so and I'll leave. There's no need to be so insulting when you know nothing about the situation mr fantastic.

    I've gotten all that I needed from this thread. Thanks.
    You're being very defensive. I'm pretty sure they were both trying to help you. Try reading mr fantastic's comment tomorrow and you might see what he was trying to tell you - he didn't mean to insult / scold you at all.
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  14. #14
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    I think you have a reading problem.
    A Mathematics Help Forum is NOT a “Do it for me home-work” service.
    You do understand that this is not a homework service?
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  15. #15
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    Quote Originally Posted by ImaCowOK View Post
    I do use the textbook as well as my notes. It's not as easy as that for someone who has never studied calculus before. I came here for help, not for a scolding. Is this not called "Math Help Forum"? If I have the wrong impression of what this site is for and my presence is bugging other users just say so and I'll leave. There's no need to be so insulting when you know nothing about the situation mr fantastic.

    I've gotten all that I needed from this thread. Thanks.
    When someone says
    Yep, that pretty much explains my class - homework problems on stuff we haven't been taught.
    then I don't think it's unreasonable to say that
    your problem is with the teacher and I would suggest that you discuss the matter with him/her
    As for the "If" in my statement, it is not unknown for students to, unfairly, blame a teacher for their difficulties.

    This thread is now closed.
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