Question

Find the value of 1² + 2² + 3² +4² + ......... + 13².
(a) 286
(b) 659 (c) 506
(d) 819​

Answer 1

sum of first 'n' natural numbers formula :- n(n+1)(2n+1)/6

where n is last number in the sequence

1²+2²+3²+4²+---------------+13²

= 13(13+1)(2×13 +1)/6

= 13×(14)×(27)/6

= 13×7×27/3

=13×7×9

=819

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