# Thread: domain problem

1. ## domain problem

if the domain of f(x) is (-1,1) then what is the domain of f((x+1)/(x-1))?

i don't even know how to start this problem. all i know is that x cannot be equal to 1.

2. Originally Posted by oblixps
if the domain of f(x) is (-1,1) then what is the domain of f((x+1)/(x-1))?

i don't even know how to start this problem. all i know is that x cannot be equal to 1.
The required domain will be the range of the function $y = \frac{x + 1}{x - 1}$ over the interval $-1 < x < 1$. The best way of finding a range is to draw a graph.

3. What is this? A rational function?

'Cause the way I find is that you take the bottom part and whatever turns out to be zero is what makes the domain...

Did you need to rewrite it in a different notation?

$(-\infty, 1) \cup (1, \infty)$

4. Originally Posted by A Beautiful Mind
What is this? A rational function?

'Cause the way I find is that you take the bottom part and whatever turns out to be zero is what makes the domain...

Did you need to rewrite it in a different notation?

$(-\infty, 1) \cup (1, \infty)$
Read the question carefully. Your reply to it is irrelevant.

5. Originally Posted by oblixps
if the domain of f(x) is (-1,1) then what is the domain of f((x+1)/(x-1))?

i don't even know how to start this problem. all i know is that x cannot be equal to 1.
The domain of:

$g(x)=f\left( \frac{x+1}{x-1} \right)$

will be the set of all real numbers $x$ such that:

$y=\frac{x+1}{x-1} \in (-1,1)$

CB