Question

If sn = n² + 2n, then find first term & common difference?

Answer 1

Answer:

for first term put n=1 that is equal to 3 and for common difference put n=2 that is 8 then common difference = 8-3=5

Step-by-step explanation:

I hope it is helpful for you

Answer 2

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