Geometric Sequences and Series

Summary

a geometric sequence or progression, is a sequence where each term is calculated by multiplying the previous term by a fixed number.

a geometric sequence has:

a first term, a, 
a common ratio, r.

if terms of a geometric sequence are added together an geometric series is formed.

there are formulae for calculating the sum of a number of terms of a geometric sequence. an infinite geometric series can tend towards a finite number.

Key Skills

  • determine whether a sequence is geometric.
  • find the first term and the common ratio of a geometric sequence.
  • find the formula for the general term and use it to find specific terms of a geometric sequence.
  • use formulae to find the sum of terms of a geometric sequence
  • find the sum to infinity of a geometric sequence

Vocabulary

geometric sequencegeometric progressionsequence, common ratio, general term.