Question

the first term and last term of an ap are 'a'and 'l'respectively ,then the sum of its 'N' terms is​

Answer 1

Answer:

$sn = \frac{n}{2} (a + l)$

Answer 2

Answer :

sn = n/2[2a + (n-1) d ]

(or)

sn = n/2 (a + l )

proof : in the picture