#### Answer

(a) secant
(b) 3

#### Work Step by Step

(a) The average rate of change of a function $f$ between $x=a$ and $x=b$ is the slope of the ___secant___ line between $(a,f(a))$ and $(b,f(b))$.
(b) The average rate of change of the linear function $f(x)=3x+5$ between any two points is ___3___ (the slope).