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: Rate of Change

  1. Sep 21, 2013 #1
    The power delivered by a battery to an apparatus of resistance R (in ohms) is P = 2.35R /(R + 0.5)^2
    watts.Find the rate of change of power with respect to resistance for R = 9.(Round your answer to four decimal places

    2. quotient rule

    3. 2.35(9+.05)^2-2(r+.5)/(r+0.5)^4
  2. jcsd
  3. Sep 21, 2013 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    You've not applied the quotient rule correctly. You dropped a factor in the second term, and a 2.35 has been reduced to 2. it would help if you included all appropriate parentheses. Why have you substituted r = 9 in some places but not in others?
  4. Sep 21, 2013 #3


    User Avatar
    Science Advisor

    What you have written is (I think - you appear to have substituted R=9 in some places but not others):[tex]2.35(R+0.5)^2-\frac{2(R+0.5)}{(R+0.5)^4}[/tex]which I don't think is right. Even assuming that you meant [tex]\frac{2.35(R+0.5)^2-2(R+0.5)}{(R+0.5)^4}[/tex]I still don't think this is right. I was taught that the quotient rule as[tex]d\frac{u}{v}=\frac{vdu-udv}{v^2}[/tex]Perhaps you could show us what you think [itex]u, v, du, dv[/itex] are?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted