## Algebra and Trigonometry 10th Edition

$y$ is a function of $x$
Solve the equation for $y$: $x^2-y=9$ $-y=-x^2+9$ $y=x^2-9$ So, for each value of $x$ in the domain we will find one and only one value of $y$. For example, if $x=5$ $y=5^2-9=25-9=16$