n → ∞ lim n 4 + 8 n 3 n ( 1 + 4 + 9 + 1 6 + . . . . + n 2 ) = ?
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Yes, the conventional methods works. Good job!
lim n → ∞ n 4 + 8 n 3 n ( 1 + 4 + 9 + 1 6 + . . . + n 2 ) = lim n → ∞ 1 + n 8 n 3 1 ∑ k = 1 n k 2 = lim n → ∞ n 1 ∑ k = 1 n ( n k ) 2 = ∫ 0 1 x 2 d x = 3 1 = 0 . 3 3 3 . . . ≈ 0 . 3 3
Fascinating approach! You have used a different method that doesn't implore the identity j = 1 ∑ n j 2 = 6 1 n ( n + 1 ) ( 2 n + 1 ) .
Nice! Using Riemann Sum, one could conclude that the leading coefficient of the polynomial of k = 1 ∑ n k x is x + 1 1 for some positive integer x .
Can you explain how did you go from n → ∞ lim n 1 k = 1 ∑ n ( n k ) 2 to ∫ 0 1 x 2 d x ?
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But I kind of get the idea. Thanks.
both beautiful solutions.
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Using this formula for the sum of squares:
lim n → ∞ n 4 + 8 n 3 n ( 1 + 4 + 9 + 1 6 + … + n 2 )
= lim n → ∞ 6 ( n 4 + 8 n 3 ) n 2 ( n + 1 ) ( 2 n + 1 )
= lim n → ∞ 6 n 4 + 4 8 n 3 2 n 4 + 3 n 3 + n 2
= lim n → ∞ 6 + n 4 8 2 + n 3 + n 2 1
= 6 2 ≈ 0 . 3 3 .