If $\displaystyle {f{{\left({x}\right)}}}={x}+{6}$ and $\displaystyle {g{{\left({x}\right)}}}={x}-{6}$,
(a) $\displaystyle {f{{\left({g{{\left({x}\right)}}}\right)}}}=$ Preview Question 6 Part 1 of 3  
(b) $\displaystyle {g{{\left({f{{\left({x}\right)}}}\right)}}}=$ Preview Question 6 Part 2 of 3  
(c) Thus $\displaystyle {g{{\left({x}\right)}}}$ is called an function of $\displaystyle {f{{\left({x}\right)}}}$