SOLUTION: Calculate the average rate of change between x = 4 and x = 8 for the function: f(x) = 12 + 4/5x I have been stuck on this problem for awhile and cannot figure out how to so

Algebra ->  Linear-equations -> SOLUTION: Calculate the average rate of change between x = 4 and x = 8 for the function: f(x) = 12 + 4/5x I have been stuck on this problem for awhile and cannot figure out how to so      Log On


   

Question 1175147: Calculate the average rate of change between x = 4 and x = 8 for the function:
f(x) = 12 + 4/5x

I have been stuck on this problem for awhile and cannot figure out how to solve it.
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

the average rate of change of f%28x%29+over an interval [a,b] is the slope of the
secant line connecting the 2 points (a,f%28a%29) and (b,f%28b%29)
average rate of change =%28f%28b%29-f%28a%29%29%2F%28b-a%29
given:
x+=+4+and x+=+8 for the function: f%28x%29+=+12+%2B+%284%2F5%29x
first find point (a,f%28a%29) if+a=x=4
f%284%29+=+12+%2B+%284%2F5%294=76%2F5 => (4,76%2F5)
find point (b,f%28b%29) if a=x=8
f%288%29+=+12+%2B+%284%2F5%298=92%2F5+=> (8,92%2F5)
average rate of change =%2892%2F5-76%2F5%29%2F%288-4%29=%2816%2F5%29%2F4=4%2F5
so, average rate of change is 4%2F5