X/a=0.5
y/a=0.5
X+y/a
a=2
X=1
y=1
x+y=a(1)
1+y=2(1)
y=2-1
y=1
You have to replace d woth 3 in formula
7d^2+10=7*(3)^2+10=7*9+10=63+10=73
d is the correct answer
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.