Final answer:
The sum of the arithmetic sequence 3, 9, 15, ... with 26 terms is 2028.
Step-by-step explanation:
To find the sum of an arithmetic sequence, you can use the formula:
Sum = (n/2)(2a + (n-1)d)
where n is the number of terms, a is the first term, and d is the common difference. In this case, the first term (a) is 3, the common difference (d) is 6, and the number of terms (n) is 26. Plugging these values into the formula, we get:
Sum = (26/2)(2(3) + (26-1)(6)) = 13(6 + 25(6)) = 13(6 + 150) = 13(156) = 2028
Therefore, the sum of the arithmetic sequence is 2028.