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!

What is this expression equal to?

  1. Dec 22, 2016 #1
    • Member reminded to post homework-type questions in the Homework sections
    Basically i need to evaluate the limit of this expression ##\lim \sqrt[3]{n^6-n^4+5}-n^2=?## I want to know if this is correct and why:
    ##\lim \sqrt[3]{n^6-n^4+5}-n^2=\lim \sqrt[3]{n^6-n^4+5}-n^2*\frac{(\sqrt[3]{n^6-n^4+5})^2+n^2\sqrt[3]{n^6-n^4+5}+n^4}{(\sqrt[3]{n^6-n^4+5})^2+n^2\sqrt[3]{n^6-n^4+5}+n^4}=\lim \frac{n^6-n^4+5-n^6}{(\sqrt[3]{n^6-n^4+5})^2+n^2\sqrt[3]{n^6-n^4+5}+n^4}##
    Why does the above fraction equals that? Is that an identity of some kind?
     
  2. jcsd
  3. Dec 22, 2016 #2

    berkeman

    User Avatar

    Staff: Mentor

    Is this a schoolwork question? If so, I can move it to the Homework Help forums.
     
  4. Dec 22, 2016 #3

    Math_QED

    User Avatar
    Homework Helper

    Do you know the identity:

    ##a^3 - b^3 = (a - b)(a^2 + ab + b^3)##?
     
  5. Dec 22, 2016 #4

    ehild

    User Avatar
    Homework Helper
    Gold Member

    You meant ##a^3 - b^3 = (a - b)(a^2 + ab + b^2)##.
     
  6. Dec 23, 2016 #5
    Its not exactly a homework problem but an already finished problem but i didnt understand that part so was looking for the identity. Thanks
     
  7. Dec 23, 2016 #6

    Math_QED

    User Avatar
    Homework Helper

    Ah thanks for correcting the typo.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: What is this expression equal to?
  1. What is u equal to? (Replies: 3)

Loading...