Multiple Choice Question (MCQ)

If the sum of n terms of an arithmetic progression is 2n^2 +5n, then its nth term is

  1. ×

    4n-3

  2. ×

    3n-4

  3. 4n+3

  4. ×

    3n+4

Collected in the board: Arithmetic sequence

Steven Zheng posted 12 hours ago

Answer

  1. Since the sum of n terms of an arithmetic progression is 2n^2 +5n

    S_n = 2n^2 +5n

    then

    S_{n-1} = 2(n-1)^2+5(n-1)

    a_n = S_n-S_{n-1}

    =2n^2 +5n- 2(n-1)^2+5(n-1)

    =4n+3

    Therefore, C is correct

Steven Zheng posted 12 hours ago

Scroll to Top