Question

What is the formula for the arithmetic sequence if the sum of the same sequence is
given by Sn = 2n + 3n^2?​

Answer 1

Step-by-step explanation:

substitute n=1 to get a1

a1= 2.1 + 3(1)^2

= 2 +3

= 5

put n=2

S2 = a1 +a2

= 2(2) + 3(2)^2

= 4 + 12

= 16

this means

5 + a2 = 16

a2= 11

the a.p is 5,11,17...