Final answer:
To find the film length that received the highest rating, determine the maximum value of the rating function R(t)= t^2 + 100 - 20t. The film length that received the highest rating is 10 minutes.
Step-by-step explanation:
To find the film length that received the highest rating, we need to determine the maximum value of the rating function R(t)= t^2 + 100 - 20t. One way to find the maximum value is by finding the critical points of the function, which occur when the derivative is equal to zero. So, let's find the derivative of R(t): R'(t) = 2t - 20. Setting this equal to zero, we have 2t - 20 = 0. Solving for t, we get t = 10. Since the second derivative is positive at t = 10, we can conclude that this critical point is a maximum. Therefore, the film length that received the highest rating is 10 minutes.