Question

why cant first differences be used to tell if the following data is linear? (1,6), (5,10), (7,14), (10,18) choose the correct answer below. a. the difference between inputs is not constant. b. the first differences are not equal. c. the difference between inputs is constant. d. the inputs and output values are all positive.

Explanation:

First differences (changes in outputs) can only test for linearity if the input differences are constant. Here, calculate input differences: $5-1=4$, $7-5=2$, $10-7=3$. These are not constant, so first differences can't be used to assess linearity.

Answer:

A. The difference between inputs is not constant.