Answer
First one :
(f x g) (x) = f(g(x). You use g(x) and substitute it in to f(x).
For example if g(x) is 4, and f(x) is 2x, then f(x) is 8.
Second :
fg(x) is the multiplication of the functions of f(x) and g(x) to create an entirely new function. Ex. F(x) is 2x and g(x) is 3x, thus gf(x) is 6$x^{2}$
Work Step by Step
First one :
(f x g) (x) = f(g(x). You use g(x) and substitute it in to f(x).
For example if g(x) is 4, and f(x) is 2x, then f(x) is 8.
Second :
fg(x) is the multiplication of the functions of f(x) and g(x) to create an entirely new function. Ex. F(x) is 2x and g(x) is 3x, thus gf(x) is 6$x^{2}$