1. Let's start by understanding what a function is. A function is a relation between a set of inputs and a set of possible outputs where each input is related to exactly one output. 2. The general form of a function is $f(x)$, where $x$ is the input and $f(x)$ is the output. 3. For example, if $f(x) = 2x + 3$, then for each value of $x$, you can find the corresponding value of $f(x)$ by substituting $x$ into the expression. 4. Important rules: - Each input $x$ has exactly one output $f(x)$. - Functions can be linear, quadratic, polynomial, exponential, etc. 5. Let's evaluate $f(2)$ for $f(x) = 2x + 3$: $$f(2) = 2(2) + 3 = 4 + 3 = 7$$ 6. So, when the input is 2, the output is 7. 7. You can also graph functions by plotting points $(x, f(x))$ on the coordinate plane. If you have a specific function or problem, please share it and I can help you step-by-step!