Pre-cal FoG GoF question

**tjjones3** · September 22nd 2008, 03:29 PM

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!!

**o_O** · September 22nd 2008, 04:44 PM

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

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

Simply replace x with the function and simplify it.

**tauro** · January 20th 2010, 07:41 PM

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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