Write the Word or Phrase That Best Completes Each Statement $$3 + \frac { 3 } { 4 } + \frac { 3 } { 16 } + \ldots + \frac { 3 } { 4 ^ { n - 1 } } = 4 \left( 1 - \frac { 1 } { 4 ^ { n } } \right)$$

Essay

Write the word or phrase that best completes each statement or answers the question. Use mathematical induction to prove that the statement is true for every positive integer n.
- $$3 + \frac { 3 } { 4 } + \frac { 3 } { 16 } + \ldots + \frac { 3 } { 4 ^ { n - 1 } } = 4 \left( 1 - \frac { 1 } { 4 ^ { n } } \right)$$