420+86+109=615 I hope this helps you
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Given :
The percent of concentration of a certain drug in the bloodstream x hours after the drug is administered is given by
.
To Find :
Find the time at which the concentration is a maximum. b. Find the maximum concentration.
Solution :
For maximum value of x, K'(x) = 0.

Since, time cannot be negative, so ignoring x = -3 .
Putting value of x = 3, we get, K(3) = 15/( 9 + 9) = 5/6
Therefore, maximum value drug in bloodstream is 5/6 at time x = 3 units.
Hence, this is the required solution.
To make the equation easier so that you don't have to use fractions.