Find the sum of the arithmetic series given a1=9, d=3, and n=14. A. 797
B. 399
C. 1594
D. 798

B) 399

Step-by-step explanation:

We want to find the sum of the arithmetic series given that:

In other words, we want to find the sum of the first 14 terms of the series when the first term is 9 and the common difference is 3.

Recall that the sum of an arithmetic series is given by:

Where n is the amount of terms, a is the first term, and xₙ is the nth or last term.

We will need to find the last term. We can write a direct formula. The general form of a direct formula is given by:

Since the initial term is 9 and the common difference is 3:

Then the 14th or last term is:

Then the sum of the first 14 terms is:

Our answer is B.

where are the choices?

70

step-by-step explanation: