Question

Determine whether the formula describes y as a function of x. y=9x-1. Explain your reasoning

Answer 1

Yes. A function is defined as having only one y value for each x value. Have you heard of the vertical line test? This equation will pass the vertical line test. No matter what x values we put in, we will never get repeated y values.
Also, if you have no idea what I am talking about, think about this: This equation will make a straight line. Every straight line is a function (unless it goes straight up and down).