Ask Me Help Desk

Ask Me Help Desk (https://www.askmehelpdesk.com/forum.php)
-   Math & Sciences (https://www.askmehelpdesk.com/forumdisplay.php?f=402)
-   -   Derivative Issues (https://www.askmehelpdesk.com/showthread.php?t=344969)

  • Apr 22, 2009, 08:00 PM
    iammario08
    Derivative Issues
    Hello everyone! So my professor gave us 100 derivative problems for our review guide, and I am not sure how to do these ones, please help!

    For these you have to find the derivative:

    f(x) = ln(9 x+2)

    h(x) = e^(x+38)

    g(x) = 18^x

    g(x) = (5 x^2 -7x)ln(x)

    g(x) = (4 x- 6)^(0.5) ln(x)

    h(x) = ln[(3x+1)/(4x-4)]

    s(x) = ln(7 x - 5)^1.3

    s(x) = log_3(9 x^2+4 x)

    r(x) = [ln(38 x^2)]^2

    r(x) = ln(x+4)+9 x^3 e^x

    r(x) = e^(6 x+5)

    r(x) = e^(5 x^2-6 x+1/x)

    t(x) = 3^(6 x-2)


    Find equation of the straight line tangent to the following curve at the point where x = 1. (Round all coefficients to two decimal places.) Use graphing technology to check your answer by plotting the given curve together with the tangent line.
    y = ln sqrt(5 x^2+6)

    Thanks a bunch!
  • Apr 23, 2009, 05:38 AM
    Perito





    So, basically all you need is the above and the chain rule.

    For the first one, f(x) = ln(9 x+2),



    since

  • Apr 23, 2009, 09:26 AM
    Unknown008

    Huh, Perito, you missed on thing there.

    The derivative of ln (9x+2) is 9/(9x+2)

    Ok, I'll post the general way to differenciate those types of equations:

    For your derivative will be when e is exponential.

    For your derivative will be when ln is any logarithm (ie ln and log)

    EDIT::: Corrected the Sorry, was tired... with that MUN... rahhhh!
  • Apr 23, 2009, 10:41 AM
    Chris-infj

    If y = ln [f(x)], then, dy/dx = f'(x)/f(x) where

    but if y = log_3 [f(x)] then dy/dx = [ f'(x)/f(x) ] ln(3). Where log_3 is log to base 3.
  • Apr 23, 2009, 12:09 PM
    Perito
    Double post? How did I do that?
  • Apr 23, 2009, 12:10 PM
    Perito

    Oops. I thought correctly, I just wrote it wrong.

    I did have



    ;)
  • Apr 25, 2009, 04:11 PM
    galactus
    Quote:

    Find equation of the straight line tangent to the following curve at the point where x = 1. (Round all coefficients to two decimal places.) Use graphing technology to check your answer by plotting the given curve together with the tangent line.
    y = ln sqrt(5 x^2+6)
    Find the derivative of the given function and plug in x=1 to find the slope, m.

    Plug in x=1 into the function as it is to find y. You are given x=1.

    Plug all those into y=mx+b and solve for b. You're done.

    To find the derivative of , use the chain rule.

    Rewrite as using the log laws.

    The derivative of the inside is

    Since the derivative of ln(x) = 1/x, then we have

    Multiply them:



    The worst part is over... finish up?

  • All times are GMT -7. The time now is 02:01 PM.