Results 1 to 4 of 4

Math Help - rational function, polynomial function or some other function

  1. #1
    Newbie
    Joined
    Sep 2010
    Posts
    12

    rational function, polynomial function or some other function

    Determine if these functions are rational function, polynomial function or some other function and why.

    1.) f(x)=2x^-3+5x^-2+6
    2.) f(t)=2t^2+t^1/3
    3.) f(r)=Gr/(r^3-8)

    Thanks
    Last edited by happy8588; September 14th 2010 at 02:04 PM.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Oct 2009
    Posts
    5,501
    Thanks
    765
    The sum, product, and ratio of rational functions are again rational functions, as are constants and x. Therefore, 1) is a rational function.

    In 2), do you mean f(t)? Note that the cubic root is not a rational function.

    I am not sure how to parse 3): is it (Gr / (r^3)) - 8? Then why not (G / r^2) - 8? Or is it Gr / (r^3 - 8)? Also, I guess it should be f(r). In any case, the same reasoning as in 1) applies.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Sep 2010
    Posts
    12
    in 2.) I do you mean f(t) I typed the wrong variable in.
    3..) f(r)=Gr / (r^3 - 8) However how is it a rational number. if i put r as 2 it would not be valid.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor
    Joined
    Oct 2009
    Posts
    5,501
    Thanks
    765
    3..) f(r)=Gr / (r^3 - 8) However how is it a rational number. if i put r as 2 it would not be valid.
    If parentheses are like this, then the question why Gr / r^3 is not simplified to G / r^2 does not arise. This is not a rational number, but a rational function because it is a ratio of two rational functions, in fact, of two polynomials. (I assume that Gr is the product of a constant G and r.)
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 2
    Last Post: March 20th 2011, 01:29 AM
  2. Replies: 3
    Last Post: October 12th 2009, 06:40 AM
  3. Replies: 1
    Last Post: March 24th 2009, 09:42 AM
  4. Homework help with Polynomial and Rational Function
    Posted in the Pre-Calculus Forum
    Replies: 11
    Last Post: November 3rd 2007, 06:26 PM
  5. Help with Polynomial and Rational Function
    Posted in the Pre-Calculus Forum
    Replies: 3
    Last Post: November 2nd 2007, 06:52 PM

Search Tags


/mathhelpforum @mathhelpforum