the equation y = mx + b as defining a linear function, whose graph is a
straight line; give examples of functions that are not linear.
a function to model a linear relationship between two quantities.
Determine the rate of change and initial value of the function from a
description of a relationship or from two (x, y) values, including
reading these from a table or from a graph. Interpret the rate of change
and initial value of a linear function in terms of the situation it
models, and in terms of its graph or a table of values.