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

Definite integral

  1. Dec 11, 2008 #1
    there's a que which baffles me today,so i hope any1 of you could help me to clear my doubt,here is the que:

    integrate with limit 3 on top n 1 below (3x^5 + 4x^4 + x^2)/x^3 dx ..
    so here goes my sol plz rectify me..
    SOL: 3x^2 + 4x + x^-1
    then integrate it
    x^3 + 2x^2..<<<<then what about x^-1 ???if we integrate it the denominator will become infinite so any value + infinity it will become infinity?am i wright?pl help me,thanks a lot...
  2. jcsd
  3. Dec 11, 2008 #2
    The integral of x^-1 is ln(x)... taken at the limits given, that's not infinity. You're method for solving is sound, but x^-1 is just one that you have to memorize.
  4. Dec 11, 2008 #3
    thanks a lot,i didnt thought of that..thanks...:smile:
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook