best way to find range

[jwxie]

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

find range for f(x) = sqrt of x-1

f(x) 1/x^2-1


2. Relevant equations

no....

3. The attempt at a solution

well, i know this is dumb to ask, but i am very very curious...

let say the first one, sqrt of x-1
if we want to find the range, obviously, you can tell just by looking at the function, since it is sqrt, it has to be y>0

second function, f(x)= 1/x^2-1
so i tried to use use the x-y method, you replace x with y, and y with x

so it becomes x = 1/y^2-1
now it is my range, but if i want to know the notation interval, like ( infinite, 0), then how do i solve for the range and get some actual indications for the range.

[Dick]

Your first and best bet is to draw a graph of each function. Try doing that. Find critical points, the whole bit. And when you post, try and make the nature of the function clear. 1/x^2-1 could mean either (1/x^2)-1 or 1/(x^2-1). I think you mean the latter. And I think your range for the first one should be y>=0 (i.e. include y=0).