Question

Find the 9th partial sum, s9, for the sequence 1, -1, 1, -1,....

Answer 1

The ninth partial sum:

We would determine the sequence to the ninth term:

Sn = 1, -1, 1, -1, 1, -1, 1,-1, 1,...

S₉ = 1 + (-1) + 1 + (-1) + 1+ (-1)+ 1+ (-1) +1 = 1.

S₉ = 1