Results 1 to 2 of 2

Math Help - Domain and largest/smallest integer

  1. #1
    Newbie
    Joined
    Dec 2008
    Posts
    13

    Domain and largest/smallest integer

    I don't quite understand the problem when they ask for the smallest/largest integer in the domain of a function. Am I supposed to take the limit or something?
    For example:
    Find the smallest positive integer in the domain of f(x):
    f(x) = \frac{\sin^2x}{\sqrt{x^2-28x-29}}
    Do I take the derivative and find where it's decreasing?

    and for this one:
    Given f(x) = x^2 - 27x - 28, find the largest integer in which f is decreasing.
    So I found the derivative, did the sign chart and found that it was decreasing at 13.5. Is this right?

    and for this one:
    f(x) = \frac{\sqrt{19x - x^2 - 34}}{e^x} has a domain of [a,b]. Find b-a
    So for this one, I found the zero of the top of the fraction, which was 17 and 2, and I made those two the domain, so 17-2 = 15. Is this correct?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    12,110
    Thanks
    982
    Quote Originally Posted by steveo0 View Post
    I don't quite understand the problem when they ask for the smallest/largest integer in the domain of a function. Am I supposed to take the limit or something?
    no ... just determine the domain.
    For example:
    Find the smallest positive integer in the domain of f(x):
    f(x) = \frac{\sin^2x}{\sqrt{x^2-28x-29}}

    x^2 - 28x - 29 > 0
    (x - 29)(x + 1) > 0

    x > 29 ... x < -1

    so ... what is the smallest positive integer in the domain?

    and for this one:
    Given f(x) = x^2 - 27x - 28, find the largest integer in which f is decreasing.
    So I found the derivative, did the sign chart and found that it was decreasing at 13.5. Is this right?

    largest integer? wouldn't that be 13?

    and for this one:
    f(x) = \frac{\sqrt{19x - x^2 - 34}}{e^x} has a domain of [a,b]. Find b-a
    So for this one, I found the zero of the top of the fraction, which was 17 and 2, and I made those two the domain, so 17-2 = 15. Is this correct?

    correct
    help any?
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 1
    Last Post: December 11th 2011, 09:49 AM
  2. Largest and smallest possible dimension?
    Posted in the Advanced Algebra Forum
    Replies: 3
    Last Post: April 15th 2010, 07:08 AM
  3. Replies: 1
    Last Post: October 2nd 2009, 05:32 AM
  4. Help finding the largest and smallest value
    Posted in the Calculus Forum
    Replies: 3
    Last Post: September 20th 2009, 06:25 AM
  5. Find the largest and smallest
    Posted in the Algebra Forum
    Replies: 2
    Last Post: December 18th 2007, 07:29 PM

Search Tags


/mathhelpforum @mathhelpforum