Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Divergent or convergent

  1. Feb 15, 2005 #1
    [tex]\int_9^{inf} \frac{1}{x^{6/5}}[/tex]

    first thing i did was found the integral of the function

    [tex]\frac{5}{x^{-1/5}}[/tex]

    then plug in inf(i will name it b) and 9

    [tex]\frac{5}{b^{-1/5}} - \frac{5}{9^{-1/5}}[/tex]
    now i will find the lim -> inf

    well for [tex]\frac{5}{9^{-1/5}}[/tex], it's equal to 7.759

    now for [tex]\frac{5}{b^{-1/5}}[/tex], it looks like INF, but when i try to submit my answer, it tells me that i'm wrong.

    anyone know what i'm doing wrong?
     
  2. jcsd
  3. Feb 15, 2005 #2
    The primitive function is wrong, it should be

    [tex]-\frac{5}{x^{1/5}}[/tex].
     
  4. Feb 15, 2005 #3

    dextercioby

    User Avatar
    Science Advisor
    Homework Helper

    Therefore,not only the limit,but also the numerical value for 9 is wrong...You should have written the integrand as [itex] x^{-\frac{6}{5}} [/itex].

    Daniel.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook