Question

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

Any help would be much appreciated, thank you ^^

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!