Which formula describes the following geometric sequence? Remember that n represents the term number.2, 6, 18, 54, ...
a. an = 2 · 3n - 1
b. an = 3 · 2n - 1
c. an = 2 + 3(n - 1)
d. an = 3 + 2(n - 1)

Respuesta :

The given sequence is 2, 6, 18, 54, ...

Notice that this is a geometric sequence because here we have equal common ratio.

So, common ratio : [tex] r = \frac{a_{2}}{a_{1}} [/tex]

=[tex] \frac{6}{2} [/tex]

= 3

The formula for general term of a geometric sequence is,

[tex] a_{n} =a_{1}* r^{n-1} [/tex]

Where, first term: a_{1} =2

Next step is to plug in these values in the above equation to get the formula for the given sequence.

[tex] a_{n} =2* 3^{n-1} [/tex]

Hence, the correct choice is A.

Answer:

Choice A

Step-by-step explanation: