Astudent is attempting to find a formula for the sequence below. which statement best applies to the sample mathematical work?

given the sequence 3, –9, 27, i first find the ratio of the terms. i find that the ratio is -9/3=-3 so i plug this value into the formula to get ^a n=(-3)^n-1 as a final answer.
a.
the ratio is calculated improperly.
b.
the formula does not take into account the first term of the sequence.
c.
the sequence is not a geometric sequence, so the equation used is wrong.
d.
the sample mathematical work is correct.

Answer : B

Step-by-step explanation:

Our sequence is 3,-9,27,........This is a geometric sequence. whose first terms is 3 which is generally denoted by "a" .The common ratio is find out by taking the ration of second term to the first term. In this case it would be ,

Hence r=-3  

Now the formula for the nth term of any geometric sequence is given as

=

Hence we now replace the value of  a and r  in this to find the right answer which is

Hence B option is correct as the first term is not taken into the account in this answer.

you answer is a

step-by-step explanation: