College Algebra (10th Edition)

The given equation defines $y$ as a function of $x$.
An equation defines $y$ as a function of $x$ if for every value of $x$, the equation gives only one corresponding value of $y$. Note that the given equation gives one value of y-value for each value of $x$. Example: When $x=0$: $y=2x^2-3x+4 \\y=2(0^2)-3(0)+4 \\y=0+4 \\y=4$ There is only one corresponding y-value for each value of $x$. Therefore, the given equation defines $y$ as a function of $x$.