A function is a relation mapping one set (the domain) to another (the codomain) such that every element in domain has a unique image in its co-domain.

Examples of functions would include ${\displaystyle 2x+3y=9}$, ${\displaystyle 4x+7z=8}$

function is denoted by symbol ${\displaystyle f(x)}$ or ${\displaystyle g(x)}$ where ${\displaystyle x}$ is the independent variable and function are written as ${\displaystyle f(x)=7x+9}$