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: Find a function with the same maximum and minimum? What?

  1. Nov 9, 2011 #1
    1. The problem statement, all variables and given/known data

    Name two different functions that share a maximum and minimum at -4.

    2. Relevant equations

    3. The attempt at a solution

    This is a vague question. I guess horizontal lines would be one. I can't think of another.
    A function that is always a point?

  2. jcsd
  3. Nov 9, 2011 #2


    Staff: Mentor

    Some textbooks distinguish between maximum and maximum value, and similarly for minimum and minimum value. Here maximum or minimum refer to the x-value, while maximum value or minimum value refer to the function value.

    For example, the function f(x) = x2 - 2x has a minimum of 1 and a minimum value of -1.

    As I interpret your problem, you need to find one function that has a maximum at -4 and another that has a minimum at -4.

    It wouldn't hurt to get clarification from your instructor.
  4. Nov 11, 2011 #3
    How about f(x) = -4 ?
  5. Nov 11, 2011 #4


    User Avatar
    Science Advisor

    I believe that was what zeion said in his original post. The problem is to find another function that has the same number as maximum and minimum.

    Zeion, what, exactly, are the conditions on the function? Would "f(0)= -4, f(x) not defined for any other value of x" work?
  6. Nov 11, 2011 #5


    User Avatar
    Gold Member

    This question needs two clarifications:

    1.) Maxima and Minima or actual values? (I take it as actual values, maxima and minima can't exist on a single point)

    2.) Whether the question is demanding a single equation have both maximum (values?) and minimum (values?) at x = -4 or two equation each with maximum and minimum.
    Last edited: Nov 11, 2011
  7. Nov 13, 2011 #6
    two thoughts:

    1) are discontinuous functions allowed?

    2) how about a function with a local min equal to a local max?
  8. Nov 13, 2011 #7


    User Avatar
    Gold Member

    No local Min or Max for discontinuous functions as I believe. Main is whether the min/max value or minima and maxima (which corresponds to x)
  9. Nov 14, 2011 #8


    User Avatar
    Homework Helper

    int(x) has jump discontinuities at each x ε Z, and yet, at every "step" (look at the graph) every point is considered to be both a local minimum and a local maximum.
  10. Nov 14, 2011 #9


    User Avatar
    Gold Member

    Sorry to disappoint you, there's no minima or maxima for a straight line as there is no change in slope.

    How can we differentiate a non-continuous function to find out its zero slope?
  11. Nov 14, 2011 #10


    User Avatar
    Homework Helper

    I'm going by the definitions of "local maximum" and "local minimum" in my precalculus book:
    (The book also has a similar definition for a local minimum)
    So, for the function f(x) = int(x), for any a that is NOT an integer, f(a) is both a local maximum and a local minimum of f.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook