Question

If the sum of the first n terms of an AP is 4n-n², what is the first term (S_{​​​​​​1}​​​​​)? What is the second term?

Answer 1

Given that,
Sn = 4n − n²

First term, a = S1 = 4(1) − (1)²= 4 − 1 = 3


Sum of first two terms = S2
= 4(2) − (2)²= 8 − 4 = 4

Second term, a2 = S2 − S1 = 4 − 3 = 1