Geometric Series When the terms of a geometric sequence are added, the result is a geometric series The sequence 3, 6, 12, 24, 48…gives rise to the series 3+6+12+24……… The sum of the first n terms of a geometric progression is: a(1 - rn )   1 – r

Example Sum the series 2+4+8+16+….. to 9 terms Sn = a(1 - rn ) 1 – r

Question The second term of a geometric sequence is -30 and the sum of the first two terms is -15. Find the first term and the common ratio. You need to find two equations, and then solve using simultaneous equations.

Questions Sum the following series to the number of terms indicated 2735 92.95907 -453.32031