Question

If the nth term of an arithmetic progression is 2n + 1, then the sum of its first n terms is​

Answer 1

Answer:

Step-by-step explanation:

Tₙ = 2n + 1

Sₙ = ΣTₙ

    = Σ2n + 1

     = 2Σn + Σ1              

     = 2(n)(n+1)/2 + n   (∵ Σn = n(n+1)/2 and Σ1 = n )

     = n(n+1) + n

    = n² + n + n

    = n² + 2n