Welcome to this deck on functions. Think of a function as a machine. You give it an input number, it performs an operation, and gives you back an output number. We'll explore how to write functions, how to reverse them, and how to link them together.

In maths, we use a special notation for functions. We might write 'f of x equals x plus 5'. This is written as f, then x in brackets. The 'f' is just a name for the function, like a label on the machine. The 'x' in the brackets represents the input value.

To use a function, we substitute a number in place of x. For example, if our function is f(x) = x + 5, and we want to find the output for an input of 3, we calculate 'f of 3'. We just replace every x with a 3. So, f(3) becomes 3 + 5, which equals 8.