Asked by Jelon

The fifth term of an arithmetic series is 12 and the eighth term is 3. Find the sum of the first 6 terms and also of the first 11 terms.

T5=a+4d=12
T8=a+7d=3
-3d=9
d=-3
Answered by Jelon
answer is a=24
d=-3
6 term=9
11 terms = -6