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

Increasing/ decreasing function

  1. Mar 28, 2009 #1
    Would you please help me with the question:

    The graph of derivative f'(x)= (1/4)x(x-6) is given.
    What value is greater f(-2) or f(10)?
    It is permitted to sketch f(x) using f'(x) graph, but you can not take the integral of f'(x) directly.
    Last edited: Mar 28, 2009
  2. jcsd
  3. Mar 28, 2009 #2


    User Avatar
    Science Advisor

    Is that supposed to be f'(x)= (1/4)x(x-6)? The graph of that is a parabola which is symmetric about x= 3. The distance from -2 to 3 is 5 while the distance from 3 to 10 is 7.
  4. Mar 28, 2009 #3
    Thank you for reply,
    The graph f(x) is not exactly symmetrical about x=3 since f(-2)=-3.67 while f(8)=-5.33, though the distance from 3 to -2 and 8 is the same.
    The data is taken from integral function y=(1/12)x^3-(3/4)x^2.
  5. Mar 29, 2009 #4
    Does anybody have other suggestions? Or maybe some elaboration on the symmetry idea? It is right that f(10)>f(-2), but I don't know solid proof for this unless taking integral, which is out of range of permitted tools
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook