Results 1 to 5 of 5

Math Help - Domain of a Function

  1. #1
    Newbie
    Joined
    Sep 2009
    Posts
    23

    Domain of a Function

    So I know domain implies input, but how would one go about finding the domain of a problem such as this:

    y=\frac{\sqrt{1-x}}{x}
    Follow Math Help Forum on Facebook and Google+

  2. #2
    -1
    e^(i*pi)'s Avatar
    Joined
    Feb 2009
    From
    West Midlands, England
    Posts
    3,053
    Thanks
    1
    Quote Originally Posted by SHiFT View Post
    So I know domain implies input, but how would one go about finding the domain of a problem such as this:

    y=\frac{\sqrt{1-x}}{x}
    • The denominator must never equal 0
    • Anything under a square root must be greater than or equal to 0


    In this case x \in \mathbb{R} \: , \: x \leq 1 \, , \, x \neq 0
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Member pflo's Avatar
    Joined
    Apr 2009
    From
    Albuquerque, NM
    Posts
    155
    Thanks
    7
    Quote Originally Posted by SHiFT View Post
    So I know domain implies input, but how would one go about solving a problem such as this:

    y=\frac{\sqrt{1-x}}{x}
    Two things about functions such as this one: 1) it won't exist when there is a negative inside the square root and 2) it won't exist when you're dividing by zero.

    Based on the first thing:
    1-x\ge0
    So x\le1

    Based on the second thing, the denominator cannot be zero. Since the denominator is x, x\ne0

    The domain is all real numbers less than or equal to 1 except 0.
    Last edited by pflo; September 30th 2009 at 01:24 PM.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Newbie
    Joined
    Sep 2009
    Posts
    23
    Thanks a lot guys, It's hard for me to understand a problem when I'm looking at it, but once I see the solution it makes so much sense.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Member
    Joined
    Mar 2008
    From
    A forrest
    Posts
    162
    Awards
    1
    If you get something like this, it's just  x \neq anything in the denominator that's going to make it zero.

    Since it was just plain old x, you'd think about making it zero since any number you could possibly plug in would not make the denominator zero unless it was 0 itself.

    This goes for anything like that pretty much.

    Like take for instance:

    f(x) = \frac{x+3}{x^2-9}.

    What's gonna make it zero?

    Well a negative and a positive squared is always going to end up positive and to make it zero what would you need to get make it that way? Well, you'd need some number x squared to make 9. What number x^2 = 9?   3. -3 also though too because (-3)^2 = (-3)(-3) = 9.


    f(x) = \frac{x+3}{9-9}.

    Can't divide by zero.

    x \neq 3  or -3.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. domain of function
    Posted in the Algebra Forum
    Replies: 2
    Last Post: January 21st 2010, 12:57 PM
  2. Domain of the Function
    Posted in the Pre-Calculus Forum
    Replies: 1
    Last Post: October 6th 2009, 03:11 PM
  3. Function domain
    Posted in the Algebra Forum
    Replies: 10
    Last Post: May 17th 2009, 03:16 PM
  4. help with the domain of the function
    Posted in the Pre-Calculus Forum
    Replies: 8
    Last Post: February 17th 2009, 05:09 PM
  5. domain of a function
    Posted in the Algebra Forum
    Replies: 3
    Last Post: August 17th 2008, 05:38 PM

Search Tags


/mathhelpforum @mathhelpforum