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

Question for integrals

  1. Jul 14, 2011 #1
    I've been solving this exercise and I came to a point when one function can get two different integrals:
    integral.jpg
    Am I doing something wrong? Because both functions are the same, and the integrals (indefinite) are really different. This is a huge problem, because this is almost the final step of an exercise and when I exchange the current variable (x) with the previously defined function for it, the solution is VERY different.
    **There should be a "-" in front of the last line of equation in the picture.
     
    Last edited: Jul 14, 2011
  2. jcsd
  3. Jul 14, 2011 #2

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    No, the two integrals are NOT "really different"- they are identical. |x- 1|= |1- x| so, of course, -ln(|x-1|)+ C= -ln(|1- x|)+ C.
     
  4. Jul 14, 2011 #3

    Redbelly98

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    Since you are taking the absolute value, |1-x| and |x-1| are the same.
     
  5. Jul 14, 2011 #4
    In the final expression a "-" appears, but I don't see how we can just make it go away (turn positive) when we are working with variables. The variable can be +-∞.
     
  6. Jul 14, 2011 #5

    Redbelly98

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    The final expressions both have a "-". There is no need to make it go away.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Question for integrals
  1. Integration question (Replies: 4)

  2. Integral question (Replies: 9)

  3. Integral Question (Replies: 3)

  4. Integration question (Replies: 4)

Loading...