Domain of functions

[asdfer]

Hello.

I was taking a test when my teacher was going over this stuff.

Out of six problems, I only know how to do one, which is...

f (x) = 1/ x+1
My solution is -infinity < x < infinity ; x =/= -1 because anything divided by 0 is UND.

This isn't the correct notation I'm suppose to use, I know. It's suppose to be d: { x | x < 2 or something. (Just an example, doesn't go to this problem).

I have other problems like: f(x) = 1/9-x and f(x) = sqrt (4-x), in which I have no clue how to do.

Any suggestions?

 

[pka]

\(\displaystyle f(x) = \frac{1}{{x + 1}}\mbox{ domain } ( - \infty , - 1) \cup ( - 1,\infty )\)

 

[o_O]

Just remember a few things: you can't have divide by zero nor can you take the square root of negative numbers. So just like for the 1/(x+1), you found x can be any real number besides -1. Similar reasoning should give you the domains for the other problems you posted.