How do you find the sum of the infinite geometric series 1-1/2+1/4+1/8?

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Answer 1 · 2016-01-25T20:46:51

As Alan P. indicated, this question has to be modified. I'm gonna assume that it is #-1/8# instead of #+1/8#

First you must find r, the common ratio.

You find this with the following formula: r = #t_2/t_1#

r = #(-1/2)/1)

r = #-1/2#

The ratio is therefore #-1/2#. The formula for the sum of an infinite geometric series is #s_oo = a/(1 - r)#

#s_oo = 1 / ( 1 - (-1/2)#

#s_oo = 1/(3/2)#

#s_oo = 2/3#

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