# Homework Help: Set Notation Question Very Easy

1. Jul 24, 2010

### GreenPrint

1. The problem statement, all variables and given/known data

If the domain of a function was defined for all reals except undefined at say x=3 were there was a vertical asymptote would you right
(-infinity, 3)U(3, infinity)
I'm not sure if it is union or infinity it's union right because technically they don't intersect right becaue of that one point? I just wanted to make sure... Thank You

2. Relevant equations

3. The attempt at a solution

2. Jul 24, 2010

### QuarkCharmer

That's correct interval notation saying "all real numbers except for 3". It's not "set builder notation" though?

The ")" is indicating that the numbers from negative infinity to 3 are not actually reaching 3. Likewise, the second part of the range is "(3,infinity)" showing that it does not actually reach 3, and extends to positive infinity.

If the interval note actually reached a number, you would use a "[". Suppose you have a range from -5 to 10, but not actually hiting 10 (asymptote ect), and then from 10 to infinity. It would look like
[-5,10)U(10,infinity)

Or something like {1<x<5 or 7<x<infinity}, on this one you have a definate range of numbers..
[1,5]U[7,infinity) /infinity always gets the parenthesis.

Last edited: Jul 24, 2010
3. Jul 24, 2010

### GreenPrint

Sorry I was thinking to different things while typing but thanks... hey I solved that problem lol thanks for your help!