Question

What is the explicit rule for this geometric sequence?

Answer 1

I took it, and assuming I'm reading your question right, it's D: an=2/3*9^n-1

Answer 2

The Information about Geometric sequence is:

$a_{1}=23 , a_{n}=9\times a_{n-1}$

→nth term of sequence = 9× (n-1) th term

Also , Common Ratio of a Geometric Sequence =$\frac{\text{Second term }}{\text{First term}}$

$\frac{a_{n}}{a_{n-1}}= \text{Common ratio}}=9\\a_{n}= a_{1}\times r ^{n-1}\\\\a_{n}=23\times 9^{n-1}$

Option 4 : $a_{n}= 23 \times 9^{n-1}$ is true.