If f(x)=7x2\displaystyle {f{{\left({x}\right)}}}={7}{x}-{2} and g(x)=x+27\displaystyle {g{{\left({x}\right)}}}={\frac{{{x}+{2}}}{{{7}}}},
(a) f(g(x))=\displaystyle {f{{\left({g{{\left({x}\right)}}}\right)}}}=  
(b) g(f(x))=\displaystyle {g{{\left({f{{\left({x}\right)}}}\right)}}}=  
(c) Thus g(x)\displaystyle {g{{\left({x}\right)}}} is called an function of f(x)\displaystyle {f{{\left({x}\right)}}}