Answer:
You only have four terms so n can only be 1, 2, 3 or 4!
I think you mean: What is the nth term of the sequence 15, 12, 9, 6, …?
The ellipsis (…) tells us that the sequence continues.
This is an arithmetic sequence, where the general term is: a+bn
n=1:a+b=15 [Eq. 1]
n=2:a+2b=12 [Eq. 2]
Subtracting Eq. 1 from Eq.2: b=−3
Substituting this into Eq. 1: a−3=15⇒a=18
Thus the nth term is: 18−3n
Explanation:
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