Question

Find the sum of first 25 sum of an AP, Nth term is given by n = 3n+2

Answer 1

given n = 25
and expression for term is given by n= 3n + 2

for n = 1
Tn = 3× 1 +2
T1= 5

and n = 25
T25 = 3× 25 +2
T25 = 77

and we knew that Sn = n/2×(a+l)

Sn = 25× 82/2
answer is
Sn = 1025