Question

If pth term of an A.P. is 3p-1/6, then sum of first n terms of
A.P. is
(a) n(3n+1)/12
(b) n(3n-1)/12
(c) n(3n + 1)/6
(d) n(3n-1)/6​

Answer 1

Answer:

option -A

pth term=3p-1/6

a+(p-1)d=3p-1/6

let p=1

a+(1-1)d=3*1-1/6

a+0=3-1/6

a=2/6=1/3

so,

Sn=n/2[1/3+3n-1/6]

sn=n/2[2+3n-1/6]

sn=n/12(3n+1)