9.2 Arithmetic Sequences

• A sequence whose consecutive terms have a coman difference is called an aeuthmetic sequence. 

       Example: 1, 4, 7, 10, 13, 16, 19, 22, 25....

                      This sequence has a difference of 3 between each number.

• The nth term of an arithmetic sequences 

          The nth term of an arithmetic sequence has the form: a_n = a₁ + d(n-1)
         a_{1= the first term, d=common difference
              Example: find the 4th term by using the} a_n formula 3, 8, 13, 18, 23, 28, 33,38...
          a₄ = a₁ + d(n-1)
            = 3+5(4-1)
               = 18

• The sum of an arithmetic sequence