Functions in the form of $y = f(x)$ describe various sorts of line.
In a quadratic line, for every extra unit in $x$, then $y$ increases by roughly $2x$.
A line where for every extra unit in $x$, then $y$ doubles is exponential, $y = 2^x$.
Thease can be inversed, for example:
For every doubling of $x$, then $y$ increases by $1$ is exponential, y = $log2(x)$.
What is this called with quadratic equations?