Question

The sum of first n terms of an AP is given by n^2+8n Find a and d and also find the sum of 50 terms?​

Answer 1

Answer:

Sn = n²+8n

let n = 1

1 + 8

= 9

so a = S1 = 9

let n = 2

S2 = 4 + 16

= 20

so a2 = S2-a

= 20-9

= 11

d = a2-a

= 11-9

= 2

SUM OF 50 TERMS = 2500+8x50

= 2900