# Thread: Pre-cal FoG GoF question

1. ## Pre-cal FoG GoF question

Ok I figured out how to find (FoG)(x) etc. but I am confused on how to find just plain FoG or GoF. For example f(x)=x^2+6 g(x)=sqrt(x-6). How do I find FoG GoF FoF and GoG of these?? Thank you sooo much for your time!!

2. $\displaystyle f({\color{red}x}) = {\color{red}x}^2 + 6$

So: $\displaystyle (f \circ g)(x) = f\big({\color{red}g(x)}\big) = {\color{red}g(x)}^2 + 6 = \left({\color{red}\sqrt{x -6}}\right)^2 + 6 = \hdots$

Simply replace x with the function and simplify it.

3. Originally Posted by tjjones3
Ok I figured out how to find (FoG)(x) etc. but I am confused on how to find just plain FoG or GoF. For example f(x)=x^2+6 g(x)=sqrt(x-6). How do I find FoG GoF FoF and GoG of these?? Thank you sooo much for your time!!
OK, start with the inside [eg if it'd FoG then start with G, if it's GoF then start with F. ] You will now have a solution for the inside. NOW when ever you see an X in the outside, substitute your solution.
Bingo !!

Good luck.

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