Calculus help?

Discussion in 'Homework Help' started by Bigcountry, Dec 6, 2008.

  1. Bigcountry

    Thread Starter AAC Fanatic!

    Jul 4, 2008
    I am having a hard time putting the differentiation equation together maybe someone could point me the in right direction. here is the problem :

    A particular factory manufactures n units per month. Each unit sells for c dollars. The number of units sold varies with the selling price according to


    and the monthly operating cost of the factory is given by

    The monthly profit

    is the maximum when the unit selling price is
    (1) $42
    (2) $36
    (3) $420
    (4) $90

    I am just having a hard time getting the equation for it. I guess I am stuck deep just need a kick start.

    thanks for any help anyone could give me some advice.
    Last edited: Dec 6, 2008
  2. blazedaces

    Active Member

    Jul 24, 2008
    Well, maybe the following will help you:

    You want the maximum dependent variable profit P in terms of the independent variable unit price c.

    Let me ask you. If you wanted to find the local max/min of a function y(x) how would you go about doing that?

    Hope this helped. Good luck,

  3. hitmen

    Active Member

    Sep 21, 2008
    Play arond with eqn until you can express P in terms of c only. You shld get a quadratic equation.

    Thereafter find DP/Dc when it is 0. you shld get the answer.
  4. Bigcountry

    Thread Starter AAC Fanatic!

    Jul 4, 2008
    thanks for your (the two of you) help. I was heading in the right direction. Just wasn't sure. it is hard to do problems with a flashlight in the dark. I know I made a couple of small mistakes.
  5. studiot

    AAC Fanatic!

    Nov 9, 2007
    The correct answer is $36 if that helps.