This is the sum of a converging infinite geometric series, so it can be written as a/(1-r) where a = 6 (the first term) and r = -1/2 (the common ratio). So the sum is 6/(3/2) = 4.
This is the sum of a converging infinite geometric series, so it can be written as a/(1-r) where a = 6 (the first term) and r = -1/2 (the common ratio). So the sum is 6/(3/2) = 4.