SOLUTION: The effectiveness of a television commercial depends on how many times a viewer watches it. After some experiments an advertising agency found that if the effectiveness E is measur

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Question 906157: The effectiveness of a television commercial depends on how many times a viewer watches it. After some experiments an advertising agency found that if the effectiveness E is measured on a scale of 0 to 10, then
E(n) = +%282%2F3%29n+-+160n%5E2+
A beter view: http://i.imgur.com/kG6LIka.png
where n is the number of times a viewer watches a given commercial. For a commercial to have maximum effectiveness, how many times should a viewer watch it? ____ times
Answer by MathLover1(20849) About Me  (Show Source):
You can put this solution on YOUR website!
as I can see on image, you have this
E%28n%29+=++%282%2F3%29n+-+%281%2F60%29n%5E2+
For this problem, E(n) is a function of n. We're trying to find the maximum value of E(n).
Assuming this is for a pre-calculus or calculus course, they probably want you to take the derivative.
So the derivative is:
E'%28n%29+=+2%2F3+-+%281%2F60%29n
The maximum then occurs when 2%2F3+-+%281%2F60%29+n+=+0.
So +%281%2F60%29+n+=+2%2F3, and n+=%282%2F3%29%2F%281%2F60%29=+120%2F3 or n+=+40.