How do you find the sum of the infinite geometric series 1/2 - 1/6 + 1/18 - ...? Precalculus Series Infinite Series 1 Answer Konstantinos Michailidis Nov 25, 2015 The common ratio is #r=-1/3# and the infinite sum equals to #S=a_1*(1/(1-r))# where #a_1=1/2# hence #S=3/8# Answer link Related questions What are some examples of infinite series? Can an infinite series have a sum? What are some examples of convergent series? What are common mistakes students make with infinite series? How do I use an infinite series to find an approximation for pi? How do I find the sum of the infinite series 1 + #1/5# + #1/25# +... ? How do I find the sum of the infinite series #1/2# + 1 + 2 + 4 +... ? What are some examples of divergent series? How do you find the sum of the infinite geometric series 1/2+1/4+1/8+1/16..? How do you find the sum of the infinite geometric series 3-1+1/3...? See all questions in Infinite Series Impact of this question 4573 views around the world You can reuse this answer Creative Commons License