Question

are composition of two functions and product of two function same ? is it true f(g(X))=F(x)G(x)?

Answer 1

Nooo, you're not multiplying them or else it would tell you to.
f(g(x)) means you are replacing x in f(x)'s equation with g(x) and solving.
Hope this helps! :)

Answer 2

but real valued function are equal why?