Question

Which of the following is the formula for this geometric sequence?
1, -3, 9, -27,...

an = -1(3)n-1
an = 1(-3)n-1
an = 3(-1)n-1
@vinnv226 will you explain this in steps?

Answer 1

@mebs

Answer 2

It would be like this take the second term divide by the first

-3/1 = -3

than take the 4th term and divide by the 3rd

-27/9 = -3

so r = -3

\[an = ar ^{n-1}\]

so it would be the second one ...

Answer 3

thx