Consider the function [math]f(x) = x^2 – 81[/math], its graph, and the constant [math]k = 3[/math]. What is [math]f(k • x)[/math]? How do the vertices and the [math]x[/math]-intercepts of [math]f(x)[/math] and [math]f(k • x)[/math] compare?
[list=1] [*]Substitute the value of [math]k[/math] into the function. [*]Using a graphing calculator, graph the two functions on the same coordinate plane. [*]Compare the graphs. [/list]