Composite functions are 2 (or more) functions carried out in sequence.

Let's say that f(x) = x + 1 and g(x) = x² - 3

fg(x) means carry out g(x) first and then put your output into f(x). The first function you need to deal with is th one that is next to (x) and work through them from left to right.

fg(5) would be:

First find g(5).

g(5) = 5² - 3 = 25 - 3 = 22

Now put your output into f(x)

f(22) = 22 + 1 = 23

So fg(5) = 23.

If we change the order, the answer will be different, so always check carefully which function you need to start with.

gf(5) would go like this

f(5) = 5 + 1 = 6

g(6) = 6² - 3 = 36 - 3 = 33

gf(5) = 33