Question

given f(x)=5-x/x+5 and g(x)=x+4 find (fog)(x)

do I just replace g(x) into fx(x) where the x's are?

Answer 1

(fog)(x) = f(g(x))
Take f(x) = 5-x/x+5
f(g(x)) means everywhere that x occurs, replace it by g(x) or by (x+4)

Answer 2

1-x/x+9
would that be the correct answer?

Answer 3

Can you write f(x) using the equation editor so it is clearer?

Answer 4

oh yes sorry

Answer 5

\[f(x)=\frac{ 5-x }{ x+5 }\]

Answer 6

would turn into \[f(x)= \frac{ 5-(x+4) }{ (x+4) +5}\]

Answer 7

Okay when writing such expression without the equation editor you should use parenthesis:
f(x) = (5 - x) / (x + 5).

Yes, your answer for f(g(x)) is correct, except use parenthesis when not using equation editor: f(g(x)) = (1 - x) / (x + 9)

Answer 8

ohhh okay thank you

Answer 9

and if im asked to find:g ( f (9) ). I would plug 9 into g(x)?

Answer 10

Look at the innermost function first.
Find f(9) by plugging 9 into f(x).
Then plug that value into g(x) to get g(f(9))

Answer 11

ohhh that's why there is ))
im going to post another one =)

Answer 12

yes. okay.