The formula for any geometric sequence is a n = a 1 · r n - 1, where a n represents the value of the nth term, a 1 represents the value of the first term, r represents the common ratio, and n represents the term number. What is the formula for the sequence -3, -6, -12, -24, ...?
an = -3 · 2n - 1
an = -3 · (-2)n - 1
an = 2 · (-3)n - 1
an = -2 · (-3)n - 1

Question

The formula for any geometric sequence is a n = a 1 · r n - 1, where a n represents the value of the nth term, a 1 represents the value of the first term, r represents the common ratio, and n represents the term number. What is the formula for the sequence -3, -6, -12, -24, ...?
an = -3 · 2n - 1
an = -3 · (-2)n - 1
an = 2 · (-3)n - 1
an = -2 · (-3)n - 1

pinky · Answer

any answer

welshfella · Answer

an = a1. r^(n-1)

here r = -6/-3, and a1 = -3

welshfella · Answer

so what is the value of the common ratio r ?

pinky · Answer

thanks

welshfella · Answer

are you ok to solve it now?

welshfella · Answer

One thing use the '^' to indicate an exponent. It can be confusing otherwise.