Answer :
Answer:
Step-by-step explanation:
Formula 1
Given an arithmetic sequence, we can calculate the sum of its first n terms, which we write Sn, using the formula:
Sn=n2(u1+un)
Where u1 is the first term of the sequence and un is the nth term.
So, for example, S10 refers to the sum of the first 10 terms, S250 refers to the sum of the first 250 terms, ... .