Question

if the sum of n terms of an AP be 3n²+n and its common difference is 6, then its first term is​

Answer 1

Answer:

first term = 4

Step-by-step explanation:

$= > s_{n} = 3 {n}^{2} + n \\ \\ = > \frac{n}{2} (2a + (n - 1)6) = 3 {n}^{2} + n \\ \\ = > n(2a + (n - 1)6) = 2n(3n + 1) \\ \\ = > 2a + 6n - 6 = 6n + 2 \\ \\ = > 2a = 8 \\ \\ = > a = 4$