In an arithmetic sequence, the sum of the first four sentences is 15 and the sum of the next five sentences is 30. Calculate the eleventh sentence of this sequence

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, ... .