Results 1 to 10 of 10

Math Help - [SOLVED] natural log

  1. #1
    Newbie
    Joined
    Jan 2010
    Posts
    5

    [SOLVED] natural log

    i have this equation:

    1=10*(e^x)-(e^y)

    and i need to find y-x, but i don't think i can just take the natural log of both sides?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by junior View Post
    i have this equation:

    1=10*(e^x)-(e^y)

    and i need to find y-x, but i don't think i can just take the natural log of both sides?
    to clarify, do you mean 1 = 10e^x - e^y? and was this the original problem?
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Jan 2010
    Posts
    5
    Yes.

    wait i think i got it:

    ln(1) = ln(10)+x-y ?
    Follow Math Help Forum on Facebook and Google+

  4. #4
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by junior View Post
    Yes.

    wait i think i got it:

    ln(1) = ln(10)+x-y ?
    actually no. you cannot distribute a log across a sum...
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    Jan 2010
    Posts
    5
    so this cant be simplified??
    Follow Math Help Forum on Facebook and Google+

  6. #6
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by junior View Post
    so this cant be simplified??
    to find y - x in terms other than y and/or x? no, not anyway that i am aware of. at least, not using any kind of pre-university math... which is why i asked if this was how the problem was presented originally. but you said yes. i don't see a way to get to the answer.
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Newbie
    Joined
    Jan 2010
    Posts
    5
    maybe you can still help me:

    im basically trying to solve number 6, so but im just doing the math wrong. the solution posted here does the problem by dividing, i tried subtracting the equations instead: http://www.ece.msstate.edu/~ykoshka/...Solutions).pdf

    <br />
I = I_s *(e^(V_1)/0.026)-1)  (1)

     10 I = I_s*(e^(V_2/.026)-1) (2)

    subtracting (2)-(1) i end up with this:

    10=[e^(V2/.026)-1]/(e^(v1/.026)-1)

    how do i solve this?
    Follow Math Help Forum on Facebook and Google+

  8. #8
    Newbie
    Joined
    Jan 2010
    Posts
    5
    actually nvm, i think i made a critical error


    that equation is hard to solve, unless you approximate

    <br />
e^v-1=e^v<br />
    Follow Math Help Forum on Facebook and Google+

  9. #9
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by junior View Post
    maybe you can still help me:

    im basically trying to solve number 6, so but im just doing the math wrong. the solution posted here does the problem by dividing, i tried subtracting the equations instead: http://www.ece.msstate.edu/~ykoshka/ECE4243-6243-Spring2008/HW/HW8(Solutions).pdf

    <br />
I = I_s *(e^(V_1)/0.026)-1)  (1)

     10 I = I_s*(e^(V_2/.026)-1) (2)

    subtracting (2)-(1) i end up with this:

    10=[e^(V2/.026)-1]/(e^(v1/.026)-1)

    how do i solve this?
    why don't you want to use division? it seems a lot easier to get to what you want to get to. also note that the solutions do not use the original equation, but an approximation of it. it would stil be really difficult to solve the equation as you have it. in any case, this looks like physics, and i'm not the expert on that.
    Follow Math Help Forum on Facebook and Google+

  10. #10
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by junior View Post
    actually nvm, i think i made a critical error


    that equation is hard to solve, unless you approximate

    <br />
e^v-1=e^v<br />
    right. apparently I_s is really small
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Can this problem be solved? (Natural Log)
    Posted in the Pre-Calculus Forum
    Replies: 5
    Last Post: September 1st 2010, 04:33 PM
  2. [SOLVED] Natural Log Help
    Posted in the Algebra Forum
    Replies: 1
    Last Post: April 17th 2009, 10:58 AM
  3. [SOLVED] natural log
    Posted in the Algebra Forum
    Replies: 2
    Last Post: March 9th 2009, 12:47 PM
  4. [SOLVED] Natural Logarithm
    Posted in the Pre-Calculus Forum
    Replies: 2
    Last Post: February 28th 2009, 09:23 AM
  5. [SOLVED] Natural Numbers
    Posted in the Discrete Math Forum
    Replies: 1
    Last Post: February 17th 2009, 04:15 AM

Search Tags


/mathhelpforum @mathhelpforum