Final answer:
The concentration of the drug decreases over time. The patient should wait approximately 1.0235 units of time before taking a second dose.
Step-by-step explanation:
a) To determine whether the concentration of the drug increases or decreases, we can analyze the formula f(t) = 2/t^2+3. As time (t) increases, the denominator (t^2+3) increases, causing the concentration to decrease. Therefore, the concentration of the drug decreases over time.
b) To find out how long the patient should wait before taking a second dose, we need to find the time when the concentration is below 1.25 milligrams per liter. Setting f(t) = 1.25 and solving for t, we get t = 1.0235. Therefore, the patient should wait approximately 1.0235 units of time before taking a second dose.