1. Not finding help here? Sign up for a free 30min 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!

Simple Differentials - please help?

  1. Oct 12, 2008 #1
    1. The problem
    Use Differentials to approximate (24.5)^(1/2) + (9.5)^(1/2). Compare your answer to your calculator's answer.

    2. Relevant equations

    I used z = (x)^(1/2) + (y)^(1/2)

    3. The attempt at a solution

    What I used:
    let z = (x)^(1/2) + (y)^(1/2)
    x = 25
    y = 10
    dx = 0.5
    dy = 0.5
    Using [​IMG].
    I plugged in 1/(2(x)^(1/2)) for the partial derivative w/respect to x, and 1/(2(y)^(1/2)) for the partial derivative w/respect to y. When I plug into the formula, I get 0.1290 not 8.0139 like in the calculator. What am I doing wrong?
    Last edited: Oct 12, 2008
  2. jcsd
  3. Oct 12, 2008 #2


    User Avatar
    Staff Emeritus
    Science Advisor

    You the did the derivative wrong. The derivative of xn is n xn-1, not n xn as you have.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Simple Differentials - please help?
  1. Differentiation help (Replies: 5)

  2. Differential help (Replies: 8)