A linear function is when there's a constant rate of change that occurs, and may be represented in the form of ax+b or mx+b, where b is the y-intercept or y-value when x is equal to zero and a=m, where the two represent the slope or rate of change. Also, a function can only have inputs that have one output each. If this doesn't fit the table that you were given, then you have a nonlinear function, where everything doesn't progress at a constant rate, and if you have the opposite, then you have a linear funciton.
