You have the following functions:
f(x)=2x+4
g(x)=3x²-1
In order to calculate the operation function composed f ° g, that is f(g(x)), you take into account that the function g(x) is the domain of f(x). This means that you replace g(x) where x is in the function f. You proceed as follow:
f(x)°g(x) = f(g(x)) = 2(3x²-1) + 4 use distribution property
= 2(3x²)-2(1)+4
= 6x² - 2 + 4
= 6x² + 2
Hence, the composed function f(g(x)) is equal to 6x² + 2
