Question

Let f be defined as follows.
y = f(x) = x^2 - 4 x

(a) Find the average rate of change of y with respect to x in the following intervals.

from x = 5 to x = 5.5
For some reason I keep getting this wrong. The way I did it was: f((5.5)-f(5))/(x2-x1)= 22-5/5.5-5=34 This is wrong, could someone show me what I'm doing wrong?

Answer 1

for f(5.5) I got 8.25
http://www.google.ca/search?hl=en&q=5.5%5E2+-+4*5.5&btnG=Search&aq=f&aqi=&aql=&oq=

Answer 2

You probably had a typo in the formula, which should read:
( f(x2)-f(x1) ) / ( x2-x1 )

For the interval [5,5.5]
(f(5.5)-f(5))/(5.5-5)
=(8.25-5)/(5.5-5)
=6.5

Post again if you still have problems.