Question

What is the sum of the first 25 terms of the sequence 3, 17, 31, 45, ... ?

Answer 1

Step-by-step explanation:

the given sequence is in AP

therefore,a=3. d=17-3=14. n=25

since Sn=

$\frac{n}{2} (2a + (n - 1)d) \\ = \frac{25}{2} (2 \times 3 + (25 - 1)14) \\ = \frac{25}{2} (6 +336) \\ = \frac{25}{2} (342) \\ = 25 \times 171 \\ = 4275$