Question

The first term of an arithmetic progression is 80 and the common difference is -3. what is the greatest possible sum of the first n terms of this sequence, and for which value of n does it occur?

I need help with this question, in advance thank you :)​

Answer 1

S=157

Explanation:

an= a1+(n-1)d

a2=80+(2-1)(-3)

a2=80-3

a2=77

Sn=(a1+an)*n/2

S2=(80+a2)*2/2

S2=(80+77)*1

S2=157