Question

The nth term of an ap is 3n+1 .The sum of its first n terms is

Answer 1

Answer:

Step-by-step explanation:

nth term = 3n+1

when n= 1---- nth term =4

n=2-------7

n=3-----10

so a=1,d=3;

sum = n/2 (2a+(n-1)d)

       = n/2(8+(n-1)3)

where n= nth term