Question

what is the sum of first n even natural numbers

Answer 1

Ap--2,4,6,8.......
a-2 d- 2
sn- n/2[2a+(n-1)d]
-

Answer 2

AP = 2,4,6,8,10,12,...

a= 2 , d=2

$s_{n} \: = \frac{n}{2} (2a + (n - 1)d)\\ \\ = \frac{n}{2} (2(2) + (n - 1)(2))\\ \\ = \frac{n}{2} (4 + 2n - 2) \\ \\ = \frac{n}{2} (2 + 2n)\\ \\ = n(1 + n)\\ \\ = {n }^{2} + n$

$s_{n} = {n}^{2} + n$