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: Forgotten how to solve for square roots

  1. Apr 22, 2013 #1
    1. The problem statement, all variables and given/known data

    compute f'(x) using the limit definition.

    f(x) = [itex]\sqrt{x}[/itex]

    2. Relevant equations

    f'(x) = [itex]\stackrel{lim}{h→0}[/itex] [itex]\frac{f(x+h)-f(x)}{h}[/itex]

    3. The attempt at a solution

    Plugging in the function values gives you

    f'(x) = [itex]\stackrel{lim}{h→0}[/itex] [itex]\frac{\sqrt{(x+h)}-\sqrt{x}}{h}[/itex]

    The end result is [itex]\frac{1}{2\sqrt{x}}[/itex] according to answer key.

    I'm not sure how to go about solving. It's the square roots that are screwing me up. I have forgotten how to solve for square roots.

    I've solved 6 problems within this context before coming across this one.
  2. jcsd
  3. Apr 22, 2013 #2


    Staff: Mentor

    Try multiplying by the conjugate over itself. IOW, multiply by
    $$ \frac{\sqrt{x + h} + \sqrt{x}}{\sqrt{x + h} + \sqrt{x}}$$
  4. Apr 22, 2013 #3
    Understood. I got the answer now. Ty
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted