Answer:
t = 1.107
Step-by-step explanation:
Finding the solution using derivatives involves finding the lower zero of the quadratic that is the second derivative of the given function. That second derivative will be ...
f''(t) = 12(1.6714)t^2 -6(22.45)t +2(62.27)
= 20.0568t^2 -134.7t +124.54
= 20.0568(t -3.35796)² -101.619 . . . . rewrite to vertex form
Then f''(t) = 0 when ...
t ≈ 3.35796 -√(101.619/20.0568) ≈ 1.10706
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The solution is perhaps more easily found using a graphing calculator to find the peak of the first derivative. (See attached.) It tells us ...
t ≈ 1.107
1.1 years after the beginning of 1998 is about 1.2 months into 1999.
Rents were increasing most rapidly in early February of 1999.
