Final answer:
The notation f(x) refers to the y-value that is produced when an x-value is substituted into a function.
Step-by-step explanation:
When the value of y is changing as a function of x, a graph can be plotted or sketched using specific values for (x,y) data pairs. The vertical axis y refers to the y-value that is produced when an x-value is substituted into a function. The variable x is the independent variable, while y is the dependent variable.
For example, consider the equation y = 9 + 3x. By substituting different values of x into this equation, we can calculate the corresponding values of y and plot them on a graph. In this case, the value of y changes depending on the value of x that is being substituted into the equation.