Given the arithmetic series a1+a2+a3+a4 12 + 19 + 26 + 33 + . . + 110 what is the value of sum?

Two adjacent terms of an arithmetic sequence differ by a fixed amount - the common difference.

In this case, the terms differ by 7. So, we can write your sequence as

So, first of all, we can observe that the last term is

So, we're summing the first 15 terms of the sequence:

We can work out the sums as follows: it is trivial that

As for the other sum, we have

So, the value is

d

step-by-step explanation:

d