Question
5, (-5/2), (5/4), (-5/8). Which term of this sequence is 5/1024?
Answers
Reiny
looks like a GP, with
a=5
r= -1/2
so term(n) = ar^(n-1)
5(-1/2)^(n-1) = 5/1024
(-1/2)^(n-1) = 1/1024
I recognize 1024 as 2^10 or (-2)^10
so (-1/2)^(n-1) = (-1/2)^10
then n-1 = 10
n = 11
or, if you feel ambitious, you can simply continue the sequence until you hit 1/1024
then count the terms
a=5
r= -1/2
so term(n) = ar^(n-1)
5(-1/2)^(n-1) = 5/1024
(-1/2)^(n-1) = 1/1024
I recognize 1024 as 2^10 or (-2)^10
so (-1/2)^(n-1) = (-1/2)^10
then n-1 = 10
n = 11
or, if you feel ambitious, you can simply continue the sequence until you hit 1/1024
then count the terms
kolaam mwonuse
nyc aanu but athreku angu poraa