Question

Sn = 4n – n2

, find a & an.​

Answer 1

Answer:

this question is not clear that what you say in this question so ask the full question in your then I help you esaily

Answer 2

Answer:

given ,

Sn =n ( 4n + 1 )

= 4n^2 + n

we know that,

Tn = Sn - S(n-1)

=4n^2+n -4 (n-1)^2 - (n-1)

=4 (n^2-n^2+2n-1)+(n-n+1)

=8n - 4 + 1

= 8n -3

hence ,

Tn = 8n -3

T1 =8 (1)-3 =5

T2= 8 (2)-3 =13

so, AP is 5, 13 , 21 and so on