Hello,
if "" means multiplication then
(fg)(x)=f(x)g(x)=g(x)f(x)=(gf)(x)=(2x²+8)(5x-6)=10x^3-12x²+40x-48
if "" means composition then
(fog)(x)=f(g(x))=f(5x-6)=2(5x-6)²+8=2(25x²-60x+36)+8=50x²-120x+80
(gof)(x)=g(f(x))=g(2x²+8)=5(2x²+8)-6=10x²+40-6=10x²+34
