Question

Using the following information, find the sum of the given arithmetic series.

a1= 16, d = -9, n = 18

Answer 1

Sn = n÷2[2a+(n-1)d]

=18÷2[2(16)+(18-1)(-9)]

Sn=-1089

Explanation:

First write out the formula for sum in arithmetic series

Then substitute the given information

Then punch everything as it is together with the signs to get the answer