ELI5: Explain Like I'm 5

Function composition

Imagine you have a bunch of toys you want to play with, but to play with them, you need to follow some rules, like sorting them by color or size or putting them into specific groups. To do this, you can use different tools, like a toy box or maybe a sorting tray.

In math, we also use different tools to solve problems or analyze data. One of these tools is called a function, which is like a machine that takes in some numbers, called inputs, and gives you back some other numbers, called outputs. Just like your toy box or sorting tray, a function can help you organize and manipulate numbers in different ways to make them easier to work with.

But sometimes, you need to use more than one tool to complete a task. For example, if you want to sort your toys by color and then size, you need to use a sorting tray for each task, and then use one tray as the input for the other. This is called function composition.

Function composition is a way of chaining together multiple functions to create a new function that does multiple things at once. It's like stacking different tools on top of each other to make a new super-tool that can do more than each individual tool on its own.

In math, you write function composition using a special notation, which looks like this: f(g(x)). This means that you're applying one function, called g, to the input x, and then using the output of that function as the input for another function, called f.

For example, let's say you have two functions: g(x) = x + 3, and f(x) = 2x. If you want to combine these functions using function composition, you would write: f(g(x)) = f(x + 3) = 2(x + 3) = 2x + 6.

In other words, you're taking the input x, adding 3 to it using g(x), and then multiplying the result by 2 using f(x). This creates a new function that performs both of these operations at once.

Function composition is a powerful tool in math because it allows you to break down complex problems into simpler steps, and then combine those steps in different ways to create new solutions. Just like your toy box or sorting tray, functions can help you organize and manipulate numbers in different ways to make them easier to work with.