Question

Sum of first n natural numbers is 5 and square + 4 n find its 8 term

Answer 1

$\textbf{- Answer -}$

Given that, the sum of the first n Natural numbers

Sn = 5n² + 4n

Now,

S8 = 5 (8)² + 4 (8)

= (5 × 64) + 32

= 320 + 32

= 352

and

S7 = 5 (7)² + 4 (7)

= 5 (49) + 28

= 245 + 28

= 273

Thus, the 8th term is

= S8 - S7

= 352 - 273

= 79

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Answer 2

Heya !!!

Sn = 5N² + 4N


Therefore,

S8 = 5 × (8)² + 4 × 8

=> 320 + 32

=> 352

And,

S7 = 5 × (7)² + 4 × 7

=> 5 × 49 + 28

=> 245 + 28

=> 273



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8th term = S8 - S7

=> 352 - 273

=> 79

HOPE IT WILL HELP YOU...... :-)