1)we calculate the amount of the drug is left in the body 2 hours after the dose is administered.
t=2
A(t)=14(08)^t
A(t)=14(0.8)²=14(0.64)=8.96
Answer: after of two hours the amount of drug left in te body is 8.96 mg.
2)we calculate the time required to stay in the body 1 mg of drug.
A(t)=1
14(0.8)^t=1
ln [14(0.8)^t]=ln1
ln14+tln(0.8)=0
tln(0.8)=-ln 14
t=-ln 14 / ln (0.8)
t=11.8267...≈11.83
Answer: the time required is 11.83 hours (≈11 hours, 49 minutes, 48 seconds).