Question

if sum of n terms of an ap is 2n^2+5,then prove that last term is 4n+3

Answer 1

$sn = {2n}^{2} + 5 \\ n = 1 \\ 2 \times {1}^{2} + 5 = 2 + 5 = 7 \\ an = 4n + 5 \\ n = 1 \\ 4 \times 1 + 3 = 4 + 3 = 7$