Question

formula of sn in AP​

Answer 1

Their are two formulae of sn in AP :-

1. Sn = ${n/2}[a + an]$

2. Sn = (n/2) {2a +(n - 1)×d}

Answer 2

$Sn = \frac{n}{2}[2a + (n - 1)d]$