# Thread: function f and g

1. ## function f and g

suppose the function f and g are difined by
f(x) = x^2 + x -2 and g (x) = 1/x

which of the following is/are true?
A. g ( x^2 +3 ) = 1/x^2 + 3
B. f ( 1/x ) = 1/x^2 +x -2
C. (f/g) (x) = x^3 + x^2 -2x and D(f/g) = R

2. Originally Posted by Alexander
suppose the function f and g are difined by
f(x) = x^2 + x -2 and g (x) = 1/x

which of the following is/are true?
A. g ( x^2 +3 ) = 1/x^2 + 3
B. f ( 1/x ) = 1/x^2 +x -2
C. (f/g) (x) = x^3 + x^2 -2x and D(f/g) = R
should A. be g(x^2 + 3) = 1/(x^2 + 3)?

and what does R mean?

Do you know how to form composite functions? For instance, do you actually know how to find g(x^2 + 3) ? If so, simply find all the composite functions your self, and see whether they are true or not

3. Originally Posted by Jhevon
and what does R mean?
I believe he means $\displaystyle \mathbb{R}$.

And if you prefer the old German style, $\displaystyle \mathfrak{R}$.

4. Originally Posted by ThePerfectHacker
I believe he means $\displaystyle \mathbb{R}$.

And if you prefer the old German style, $\displaystyle \mathfrak{R}$.
yea. i realize that now. the problem was i was thinking D meant derivative (as it does when programming in maple), so i found it weird when it said D(f/g) = R. but now i realize it is talking about the domain, which makes sense, since there's no way questions of this nature would be asked in a calculus class--unless it's precalculus, in which case, derivatives still wouldn't come up