Question

What are the explicit equation and domain for a geometric sequence with a first term of 3 and a second term of −9?

an = 3(−12)n − 1; all integers where n ≥ 1
an = 3(−12)n − 1; all integers where n ≥ 0
an = 3(−3)n − 1; all integers where n ≥ 1
an = 3(−3)n − 1; all integers where n ≥ 0

Answer 1

any idea?

Answer 2

\[a_{n}=a _{1}{r^{n-1}},r \ge 1\]
\[a _{1}=first~term\]
r=common ratio
\[r=\frac{ a _{2} }{ a _{1} }\]
\[a_{2}=second~term\]