1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
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: Did i do the reduction correctly? algebra type stuff!

  1. Mar 9, 2006 #1
    Find all the values of x such that the given series would converge.

    http://cwcsrv11.cwc.psu.edu/webwork2_files/tmp/equations/fd/74dc1166ac21d3f59ee568a71eb55a1.png [Broken]
    Here is my work:
    http://img203.imageshack.us/img203/9559/lastscan3jv.jpg [Broken]

    I got it wrong but is it because i don't know how to do inequalities, or just suck in general?
    Last edited by a moderator: May 2, 2017
  2. jcsd
  3. Mar 9, 2006 #2
    What happened to the 2?

    Last edited by a moderator: May 2, 2017
  4. Mar 9, 2006 #3
    I follow you until this line: [tex]\lim_{n\rightarrow\infty}\frac{(-x)(n^2+3)}{2n^2+4n+8}[/tex]

    and then I don't see what you're doing.
  5. Mar 9, 2006 #4
    Okay from here, i'm using the rule, where u divide by the largest exponent, in this case its n^2, so u divide every term by n^2 and leave the -x alone, then u take as n->infinity. I'm using this website as my guide:

    Ooo i don't know where the 2 went lol i will do it again with the 2
    Last edited by a moderator: Apr 22, 2017
  6. Mar 9, 2006 #5
    Sweet it worked once i added the 2 lol.

    |-x|/2 < 1

    |-x| < 2
    -2 < x <2

    quick question though. is |-x| == |x|? i just assumed it was, thats how i came out with -2 < x < 2
  7. Mar 9, 2006 #6
    I was wondering why you didn't just go straight to |x|/2. And yes, I think you're answer is correct.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook