Willis analyzed the following table to determine if the function it represents is linear or non-linear. First he found the differences in the y-values as 7 – 1 = 6, 17 – 7 = 10, and 31 – 17 = 14. Then he concluded that since the differences of 6, 10, and 14 are increasing by 4 each time, the function has a constant rate of change and is linear. What was Willis’s mistake? x y 1 1 2 7 3 17 4 31 He found the differences in the y-values as 7 – 1 = 6, 17 – 7 = 10, and 31 – 17 = 14. He determined that the differences of 6, 10, and 14 are increasing by 4 each time. He concluded that the function has a constant rate of change. He reasoned that a function that has a constant rate of change is linear.