Tuesday, 25 February 2014

algebra precalculus - A geometric sequence has first term 256 and ratio 0.75. Find the smallest n for which the sum of the first n terms exceeds 1000.


A geometric sequence whose first term = 256 and whose common ratio is 0.75. Find the smallest number of n for which the sum of the first n terms of the sequence exceeds 1000.




My turn:

Sn=256(1(0.75)n)10.75>1000
nlog0.75<log3128
n<13.04 then
n=13




What is wrong with my solution because 13 does not satisfy the requires but 14 does ?


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