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: Evaluate the Limit (just confirmation)

  1. Mar 20, 2013 #1
    1. The problem statement, all variables and given/known data

    lim (cubicsquareroot(x) - 2)/(x-8)

    2. Relevant equations

    3. The attempt at a solution

    I obtained 1/12 as my final answer, after changing the variable since its in indeterminate form.
    ..let p=cubicsquareroot(x), then as x→8, p→2
    then, p^3=x

    Using this logic I obtained 1/12.

    Is this correct ?
  2. jcsd
  3. Mar 20, 2013 #2
    Precisely, Although It'd be nicer if you had done some substitutions.. Yeah is correct!
  4. Mar 20, 2013 #3
    My bad! you have! And when you reach L'Hopital's rule, revisit these questions..
  5. Mar 20, 2013 #4


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    What's a "cubicsquareroot" ?
  6. Mar 20, 2013 #5
    Assumed he meant x^(1/3) *kids today*
  7. Mar 20, 2013 #6
    lol Yeah I mean't x^(1/3). And thanks.
  8. Mar 20, 2013 #7


    Staff: Mentor

    L' Hopital's Rule is not needed in this problem.

    The OP apparently revised the original problem to this form:
    $$ \lim_{p \to 2} \frac{p - 2}{p^3 - 8}$$

    and then factored the denominator to (p - 2)(p2 + 2p + 4), and then took the limit.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted