Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Optimization (applications of Differentation) Problem

  1. Mar 14, 2010 #1
    1. The problem statement, all variables and given/known data
    The demand function for a product is modeled by


    Where p is the price per unit (in dollars) and x is the number of units. What price will yield a maximum revenue.

    2. Relevant equations

    3. The attempt at a solution

    Ok so i tried taking the derivative to start off with. it is obviously an awkward problem. The derivative i found, and this may be wrong is

    (6.72 x 10^-4)e^-1.000012x

    if that is right, where from here?
  2. jcsd
  3. Mar 14, 2010 #2


    User Avatar
    Homework Helper

    Derivative (of p with respect to x) is right except for sign.

    The problem is to maximize something. First thing you need to do is write an expression for what is to be maximized. Is it p or something else? Second step comes from calculus. Remember how to find the min or max of a function? You correctly imply that a derivative is involved, but what about the derivative?
    Last edited: Mar 14, 2010
  4. Mar 14, 2010 #3
    The derivative is used to find the critical numbers right?

    as to setting up the equation would this work.

    px = r

    and then because you cannot have two variables you must take p and substitute it with 56e^-0.000012x.

    so your new equation becomes

    56e^-.000012x (times) X

  5. Mar 14, 2010 #4


    User Avatar
    Homework Helper

    Correct, you want to maximize r = 56xe-.000012x. Also correct that derivatives are used to find critical points (but how?). So, what to you need to do with the expression for r to find its maximum? Calculate it's derivative and do what with it?
    Last edited: Mar 14, 2010
  6. Mar 14, 2010 #5
    set it equal to zero and therefore find the critical numbers?
  7. Mar 14, 2010 #6


    User Avatar
    Homework Helper

    Correct! So, set the derivative of r (with respect to x) equal to zero and solve for x. From that you can determine the optimal value for p.

    One thing to watch out for. The problem implies that an integer value for x is needed. If that's really true, you'll need to round x up and down to the nearest integer value and check r using both to find out which one produces the largest r.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook