# Math Help - Functions F(x)

1. ## Functions F(x)

Two functions are defined as

and

Find ?

Find ?

Find ?

What do I need to do?

2. ## Re: Functions F(x)

Originally Posted by leonm92
What do I need to do?
For starters, find f(-5). I assume fg(-4) means f(g(-4)). Usually one writes $(f\circ g)(4)$ where $\circ$ is the operation of function composition, or, skipping $\circ$, (fg)(4) or f(g(-4)) instead of fg(-4).

3. ## Re: Functions F(x)

ok thank you. what if theres a function like f^-1 (-2)

4. ## Re: Functions F(x)

$f^{-1}$ is a function inverse to f. Note that (not necessarily in your problem, but in general) for some y there may be several different x such that f(x) = y. In this case, it is not clear to which of those x the inverse function $f^{-1}$ should map y. Therefore, the concept of inverse function is unambiguous only if the original function is injective.

5. ## Re: Functions F(x)

let's say you want to find f(-5). to do that, compute:

(2(-5) + 9)/((-4)(-5) 5) = ?