当n趋向无穷大时,求 ((1^2+2^2+…n^2)/(n+1)^2-n/3)的极限?

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当n趋向无穷大时,求 ((1^2+2^2+…n^2)/(n+1)^2-n/3)的极限?

1^2+2^2+…n^2=n(n+1)(2n+1)/6
(1^2+2^2+…n^2)/(n+1)^2=n(2n+1)/6(n+1)
((1^2+2^2+…n^2)/(n+1)^2-n/3)= n(2n+1) - 2n(n+1)
-----------------------------
6(n+1)
=-n/6(n+1)
当n趋向无穷
-n/6(n+1) -> -n/6n = - 1/6