SOLUTION: this is a different one our instructor wrote for us. I have not a clue how to begin. at these prices it is estimated that the number of customers is related to the amount of ti

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Question 44980: this is a different one our instructor wrote for us. I have not a clue how to begin.
at these prices it is estimated that the number of customers is related to the amount of time they must wait as,
N = -5t(squared)+80t-280, where t is time in minutes. When there are 35 customers what is the estimated wait time?
Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
You don't specify but I assume that N = number of customers and t = wait time.
N+=+-5t%5E2%2B80t-280 For 35 customers, N = 35, so you can write:
-5t%5E2%2B80t-280+=+35 Subtract 35 from both sides of the equation.
-5t%5E2%2B80t-245+=+0 Use the quadratic formula to solve this quadratic equation for t: t+=+%28-b%2B-sqrt%28b%5E2-4ac%29%29%2F2a
For this problem, a = -5, b = 80, and c = -245
t+=+%28-80%2B-sqrt%2880%5E2-4%28-5%29%28-245%29%29%29%2F2%28-5%29
t+=+%28-80%2B-sqrt%286400-4900%29%29%2F-10
t+=+%28-80%2B-sqrt%281500%29%29%2F-10
t+=+%28-80%2F-10%29%2B%2838.7%2F-10%29 or t+=+%28-80%2F-10%29-%2838.7%2F-10%29
t+=+8-3.87 or t+=+8%2B3.87
You get two positive wait times:
t = 4.13
t = 11.87