Chapter 3 - Linear and Quadratic Functions - 3.1 Properties of Linear Functions and Linear Models - 3.1 Assess Your Understanding - Page 126: 21

Linear slope $=-3$

A function is linear if there is a constant rate of change of the function, which is also called the slope. Note that: $1-4=-3\\ -2-1=-3\\ -5-(-2)=-3\\ -8-(-5)=-3$ Hence, the difference of all consecutive y-values is $-3$, which means that the slope is $-3$. Thus, the function is linear.