Write the Word or Phrase That Best Completes Each Statement $$6 + 6 ^ { 2 } + \ldots + 6 ^ { n } = 6 \left( \frac { 6 ^ { n } - 1 } { 5 } \right)$$

Essay

Write the word or phrase that best completes each statement or answers the question.
Use mathematical induction to prove the following statement for all positive integers n.
- $$6 + 6 ^ { 2 } + \ldots + 6 ^ { n } = 6 \left( \frac { 6 ^ { n } - 1 } { 5 } \right)$$