Question

IfSn=n(4n+1),findtheAP.

Answer 1

Step-by-step explanation:

sn is given

so put n= 1 , so we get

S1 = 5

put n= 2 , so we get

S2 = 9*2 = 18

put n= 3, we get

S3 = 3*13= 39

S1 means sum of first term , so it is itself first term of series. first term of series = 5

S2 means sum of first two term, but first term = 5 , so second term = 18-5 = 13.

S3 means sum of first 3 terms of series ,

so third term of series = 39-(13+5) = 21.

so our A.P. is - 5,13 ,21........