Answer:
average rate of change = 2
Explanation:
since f(x) is a linear function, then the slope is the measure of the average rate of change of f(x).
note the average rate of change is constant over any closed interval.
the equation of a linear function in slope- intercept form is
f(x) = mx + c ( m is the slope and c the y- intercept )
f(x) = 2x + 4 ← is in slope- intercept form
with slope m = 2
then average rate of change = 2