Question

Sum of n terms of an arithmetic progression is 2n^2+n then the eighth term is

Answer 1

put 8 in place of n and 7 in place of n the difference will give the 8th term

Answer 2

Answer:

31

Step-by-step explanation:

$S_n=2n^2+n$

Put n =8

So, sum of first 8 terms = $S_8=2(8)^2+8 = 136$

Now substitute n = 7

So, sum of first 7 terms = $S_7=2(7)^2+7 = 105$

So, 8th term = Sum of first eight terms - Sum of first seven terms

                    = $S_8-S_7$

                    = $136-105$

                    = $31$

Hence the eighth term is 31.