Question

The graph below shows the value of Edna's profits f(t), in dollars, after t months:

graph of quadratic function f of t having x intercepts at 6, 0 and 18, 0, vertex at 12, negative 36, and passes through point 21, 41.25

What is the closest approximate average rate of change for Edna's profits from the 18th month to the 21st month?

a. Three dollars per month

b. Nine dollars per month

c. 13.75 dollars per month

d. 41.25 dollars per month

Answer 1

C) 13.75 dollars per month

Explanation:

i took the test and got it right

Answer 2

The easiest way to find the average rate of change is with the formula:
( y 2 - y 1 ) / ( x 2 - x 1 )
We have to find the average rate of change from the 18th month to the 21st month. So: y2 = 41.25, y 1 = 0, x 2 = 21, x 1 = 18;
( 41.25 - 0 ) / ( 21 - 18 ) = 41.25 / 3 = 13.75
Answer:
c. 13.75 dollars per month.