Answer is: option2
1Solution:
v(t) = et / t
Using the quotient rule:
v'(t) = (et·t − et·1) / t² = (et(t − 1)) / t²
Set the derivative equal to zero to find critical points:
v'(t) = 0 ⟹ (et(t − 1)) / t² = 0
Since et > 0 and t² > 0 for t > 0, the equation simplifies to:
t − 1 = 0 ⟹ t = 1
For t < 1 (e.g., t = 0.5):
v'(0.5) = (e0.5(0.5 − 1)) / (0.5)² = Negative
The function is decreasing.
For t > 1 (e.g., t = 2):
v'(2) = (e2(2 − 1)) / 2² = Positive
The function is increasing.
Since the function changes from decreasing to increasing at t = 1, this point corresponds to a minimum.
The velocity v attains its minimum at t = 1.
Answer: B