Write the Word or Phrase That Best Completes Each Statement $$1 + 4 + 7 + \ldots + ( 3 n - 2 ) = \frac { n ( 3 n - 1 ) } { 2 }$$

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.
- $$1 + 4 + 7 + \ldots + ( 3 n - 2 ) = \frac { n ( 3 n - 1 ) } { 2 }$$