Geometric Sequence question

[Justin218]

Does anyone know how to answer this question: http://home.earthlink.net/~justincredible218/geometric.JPG

The answer is C, but how?

 

[dighn]

the factor is -1/2
the nth term is 3/2*(-1/2)^(n-1) = 3 * (-1)^(n-1) / 2 * 2^(n-1) = 3 * (-1)^(n-1) / 2^(n)

 

[Justin218]

ooh, I get it now, thanks.