How to do composition of functions

Example: f(x) = 2x+3 and g(x) = x2

"x" is just a placeholder. To avoid confusion let's just call it "input":

f(input) = 2(input)+3

g(input) = (input)2

Let's start:

(g º f)(x) = g(f(x))

First we apply f, then apply g to that result:

Function Composition - (g º f)(x) = (2x+3)2

What if we reverse the order of f and g?

(f º g)(x) = f(g(x))

First we apply g, then apply f to that result:

Function Composition - (f º g)(x) = 2x2+3

We get a different result!  When we reverse the order the result is rarely the same.  So be careful which function comes first.

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