Question

Sum to n term of an Arithmetic progression is 2n x n+n then eighth term is

Answer 1

Answer:

Sn = 2n² + n

if n = 8, then

S₈ = 2(8)² + 8

    = 136

Therefore sum of the eight elements is 136.

Answer 2

Answer:

31

Step-by-step explanation:

Sn=2n^2+n  

Put n =8  

So, sum of first 8 terms = S8=2(8)^2+8 = 136

Now substitute n = 7

So, sum of first 7 terms = S7=2(7)^2+7 = 105  

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

                    = S8-S7  

                   = 136-105  

                   = 31  

Hence the eighth term is 31.

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