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: Interval of Convergence of Power Series with Square Root

  1. Apr 25, 2016 #1
    I'm trying to find the answer to a question similar to this posted it earlier but in the wrong section I think and not explained well.
    \sum_{{\rm n}=0}^\infty \left (-\sqrt x \right )^n \ \ \rm ?$$
    Find the interval of convergence?
    I tried using the root test and got from 0 to 1 but when I checked with Wolfram and it gave from -1 to 1 saying the absolute value would go inside the square root. Am I doing something wrong or is Wolfram making a mistake. Thanks in advance for any help.
  2. jcsd
  3. Apr 25, 2016 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Assuming ##x## is real, ##x<0## is not in the domain.
  4. Apr 25, 2016 #3
    Thank you for the help in clearing up my confusion.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted