A student 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.

Question

Sophia

Mathematics

7 February, 16:51

A student 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.

+2

Answers (1)

Know the Answer?

Doofus · Answer 1

The sample is a geometri sequencethe ratio = - 9 / 3 = - 3 = 27 / - 9 = - 3so it is clearly a geometric sequencethen the formula of a geometric sequence:

an = ar^ (n-1) where an is the n terma is the initial termr is the rationn is the number of term

an = 3 (-3) ^ (n-1) is the answer