If a formula that decribes the relationship between
$x$ and
$y$ is given in the form
$y$ = ... then
$y$ is called a function of
$x$.
In the corresponding graph
$y$ is always chosen on the vertical axis.
In the formula $y={x}^{2}+4$ $y$ is a function of $x$.
In the formula $P=0.052{v}^{3}$ $P$ is a function of $v$.
The formula $a+2b=6$ can be written in two ways:
$a=6-2b$, where $a$ is a function of $b$.
$b=3-0.5a$, where $b$ is a function of $a$.
You can enter formulas given in the form $y=\mathrm{...}$ into the graphical calculator.