F(t) = -5t^2 + 20t + 60
-5(t^2 - 4t - 12)
-5(t + 2) (t - 6)
t = -2 or t = 6
6 seconds
Given:
The arithmetic sequence is −15, −33, −51, −69.
To find:
The nth term of the arithmetic sequence.
Solution:
We have,
−15, −33, −51, −69
Here,
First term: a = -15
Common difference is



Now, nth term of an arithmetic sequence is

Substitute a=-15 and d=-18.



Therefore, the nth term of the given arithmetic sequence is
.
Answer:
51
Step-by-step explanation: