Question

Write an explicit formula that represents the geometric sequence -2,8,-32,128

Answer 1

Hello from MrBillDoesMath!

Answer:

a(n) =  (-1)^(n+1)   *   ( 2 ^ (2n+1) )                    where n = 0, 1, 2, etc.

Discussion:

-2 =   (-1) * 2^1

8 =    (+1) 2^3

-32 = (-1) * 2^5

128 = (+1)* 2^7

In general,

a(n) =  (-1)^(n+1)  *   (2 ^ (2n+1))                    where n = 0, 1, 2, etc.

Regards,  

MrB

P.S.  I'll be on vacation from Friday, Dec 22 to Jan 2, 2019. Have a Great New Year!