Question

please solve it guys​

Answer 1

Answer:

$s _n = n(n - 2)$

Step-by-step explanation:

$3 + 5 + 7 + .....upto \: n \: terms \\ \\ a _n = 2n + 1 \\ \\ a = 3 \\ \\ d = 2 \\ \\ s _n = \frac{n}{2} (2a + (n - 1)d) \\ \\ s _n = \frac{n}{2} (6 + (n - 1) \times 2) \\ \\ s _n = \frac{n}{2} (2n - 4) \\ \\ s _n = n(n - 2)$

HOPE IT HELPS