Results 1 to 2 of 2

Thread: Increasing/ Decreasing intervals

  1. #1
    Member
    Joined
    Jul 2010
    Posts
    109

    Increasing/ Decreasing intervals

    For x ∈ [−12, 11] the function f is defined by


    f(x) = x3(x + 6)^6
    On which two intervals is the function increasing (enter intervals in ascending order)?
    Find the region in which the function is positive: to
    Where does the function achieve its minimum?



    when i derived it i got

    3x^2(x+6)^6 + 6x^3(x+6)^5
    then you set it equal to zero... how do i use the algebra part now?

    I tried something like this:

    (x+6)^5 [3x^2(x+6)+ 6x^3]
    please help!



    I got all the answers now but the last....
    when does it reach it's minimum?
    Last edited by mr fantastic; Nov 14th 2011 at 05:47 PM. Reason: Title.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Prove It's Avatar
    Joined
    Aug 2008
    Posts
    12,673
    Thanks
    1865

    Re: URGENT! DUE 12 AM!! Increasing/ Decreasing intervals

    Quote Originally Posted by habibixox View Post
    For x ∈ [−12, 11] the function f is defined by


    f(x) = x3(x + 6)^6
    On which two intervals is the function increasing (enter intervals in ascending order)?
    Find the region in which the function is positive: to
    Where does the function achieve its minimum?



    when i derived it i got

    3x^2(x+6)^6 + 6x^3(x+6)^5
    then you set it equal to zero... how do i use the algebra part now?

    I tried something like this:

    (x+6)^5 [3x^2(x+6)+ 6x^3]
    please help!



    I got all the answers now but the last....
    when does it reach it's minimum?
    You are correct so far. Since you now have two factors that multiply to give 0, at least one of them must be 0.

    So (x + 6)^5 = 0 or 3x^2(x + 6) + 6x^3 = 0

    You can factorise the second equation further...
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Find intervals of f increasing/decreasing
    Posted in the Calculus Forum
    Replies: 3
    Last Post: Jul 9th 2010, 09:41 AM
  2. intervals of increasing/ decreasing
    Posted in the Pre-Calculus Forum
    Replies: 3
    Last Post: Aug 16th 2009, 08:22 PM
  3. Replies: 1
    Last Post: Nov 28th 2008, 08:12 AM
  4. Increasing/decreasing intervals of a function
    Posted in the Calculus Forum
    Replies: 1
    Last Post: Jul 15th 2008, 05:32 AM
  5. Increasing/Decreasing Intervals
    Posted in the Calculus Forum
    Replies: 1
    Last Post: Mar 25th 2008, 02:02 PM

Search Tags


/mathhelpforum @mathhelpforum