Domain = R
Range = R .............
Answer:
a. 
b. 
Step-by-step explanation:
First, we need tot find a general expression for the amount of caffeine remaining in the body after certain time. As the problem states that every hour x percent of caffeine leaves the body, we must substract that percentage from the initial quantity of caffeine, by each hour passing. That expression would be:

Then, to find the amount of caffeine metabolized per hour, we need to differentiate the previous equation. Following the differentiation rules we get:

The rate is negative as it represents the amount of caffeine leaving the body at certain time.
The 5 in x - 5 needs to be negative in the table. So, change that and make everything else in that row negative.
You are then left with 3x^2 + x - 15x - 5
Simplify to 3x^2 - 14x - 5
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A simpler form of this expression would be 19y-9