Question

the sum of an arthametic progration is sn=n²+n then A3 is​

Answer 1

Answer:

Step-by-step explanation:

Sn = n^2 + 2n

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

an = Sn - S(n-1) = n^2 + 2n - n^2 + 1 = 2n+1

First Term, a = 2*1 + 1 = 3

Second Term, a2 = 2*2 + 1 = 5

d = 5 - 3 = 2

Therefore

a = 3, d = 2 ——-> Answer

Answer 2

Given the following sequence Sn is given then find the first two terms of the sequence

Sn = n²(n+3)