2. Find the sum of the first 14 terms of the series 11 + 7 + 3 +
The common difference is -4
The 14th term is
11 -4(14 - 1) =
11 - 4(13)
11 - 52
-41
So.....the sum of the first 14 terms =
[ first term + last term] * number of terms / 2 =
[ 11 - 41 ] * 14 / 2 =
[ -30 ] * 7 =
-210
