Let f(x)=\displaystyle {f{{\left({x}\right)}}}= 6x+8\displaystyle -{6}{x}+{8} and g(x)=\displaystyle {g{{\left({x}\right)}}}= 5x2\displaystyle -{5}{x}-{2}.

Simplify:

(fg)(x)=\displaystyle {\left({f}\circ{g}\right)}{\left({x}\right)}=