1的平方加上2的平方加上3的平方加上4的平方一直加到n的平方=多少拜托了各位 谢谢 1平方加2平方加3平方一直加到n平方等于多少

n\u4e09\u6b21\u65b9\u5206\u4e4b1\u7684\u5e73\u65b9\u52a0\u4e0a2\u7684\u5e73\u65b9\u52a0\u4e0a3\u7684\u5e73\u65b9\u52a0\u4e0a4\u7684\u5e73\u65b9\u4e00\u76f4\u52a0\u5230n\u7684\u5e73\u65b9

n\u4e09\u6b21\u65b9\u5206\u4e4b1\u7684\u5e73\u65b9\u52a0\u4e0a2\u7684\u5e73\u65b9\u52a0\u4e0a3\u7684\u5e73\u65b9\u52a0\u4e0a4\u7684\u5e73\u65b9\u4e00\u76f4\u52a0\u5230n\u7684\u5e73\u65b9

=(1²+2²+3²+4²+......+n²)/n³ \u5bf9\u5417\uff1f
=[n(n+1)(2n+1)/6]/n³
=(1+1/n)(2+1/n)/6

lim(1+1/n)(2+1/n)/6=2/6=1/3

1²+2²+3²+\u2026\u2026+n²=n(n+1)(2n+1)/6\u3002\u53ef\u4ee5\u7528(n+1)³-n³=3n²+3n+1\u7d2f\u52a0\u5f97\u5230\u3002
\u8bc1\u660e\u8fc7\u7a0b\uff1a
\u6839\u636e\u7acb\u65b9\u5dee\u516c\u5f0f(a+1)³-a³=3a²+3a+1\uff0c\u5219\u6709\uff1a
a=1\u65f6\uff1a2³-1³=3\u00d71²+3\u00d71+1
a=2\u65f6\uff1a3³-2³=3\u00d72²+3\u00d72+1
a=3\u65f6\uff1a4³-3³=3\u00d73²+3\u00d73+1
a=4\u65f6\uff1a5³-4³=3\u00d74²+3\u00d74+1.\u00b7\u00b7
a=n\u65f6\uff1a\uff08n+1\uff09³-n³=3\u00d7n²+3\u00d7n+1
\u7b49\u5f0f\u4e24\u8fb9\u76f8\u52a0\uff1a
\uff08n+1)³-1=3\uff081²+2²+3²+\u00b7\u00b7\u00b7\u00b7\u00b7\u00b7+n²\uff09+3\uff081+2+3+\u00b7\u00b7\u00b7\u00b7\u00b7\u00b7+n\uff09+\uff081+1+1+\u00b7\u00b7\u00b7\u00b7\u00b7\u00b7+1\uff09
3\uff081²+2²+3²+\u00b7\u00b7\u00b7\u00b7\u00b7\u00b7+n²\uff09=\uff08n+1\uff09³-1-3\uff081+2+3+.+n\uff09-\uff081+1+1+.+1\uff09
3\uff081²+2²+3²+\u00b7\u00b7\u00b7\u00b7\u00b7\u00b7+n²\uff09=\uff08n+1\uff09³-1-3\uff081+n\uff09\u00d7n\u00f72-n
6\uff081²+2²+3²+\u00b7\u00b7\u00b7\u00b7\u00b7\u00b7+n²\uff09=2\uff08n+1)³-3n\uff081+n)-2(n+1)=(n+1)[2(n+1)²-3n-2]
=(n+1)[2(n+1)-1][(n+1)-1]=n(n+1)(2n+1)
\u6240\u4ee51²+2²+\u00b7\u00b7\u00b7\u00b7\u00b7\u00b7+n²=n\uff08n+1)\uff082n+1\uff09/6\u3002

\u6269\u5c55\u8d44\u6599\uff1a
\u7acb\u65b9\u5dee\u516c\u5f0f\u4e0e\u7acb\u65b9\u548c\u516c\u5f0f\u7edf\u79f0\u4e3a\u7acb\u65b9\u516c\u5f0f\uff0c\u4e24\u8005\u57fa\u672c\u63cf\u8ff0\u5982\u4e0b:
1\u3001\u7acb\u65b9\u548c\u516c\u5f0f\uff0c\u5373\u4e24\u6570\u7acb\u65b9\u548c\u7b49\u4e8e\u8fd9\u4e24\u6570\u7684\u548c\u4e0e\u8fd9\u4e24\u6570\u5e73\u65b9\u548c\u4e0e\u8fd9\u4e24\u6570\u79ef\u7684\u5dee\u7684\u79ef\u3002\u4e5f\u53ef\u4ee5\u8bf4\u4e24\u6570\u7acb\u65b9\u548c\u7b49\u4e8e\u8fd9\u4e24\u6570\u79ef\u4e0e\u8fd9\u4e24\u6570\u5dee\u7684\u4e0d\u5b8c\u5168\u5e73\u65b9\u7684\u79ef\u3002
2\u3001\u7acb\u65b9\u5dee\u516c\u5f0f\uff0c\u5373\u4e24\u6570\u7acb\u65b9\u5dee\u7b49\u4e8e\u8fd9\u4e24\u6570\u5dee\u4e0e\u8fd9\u4e24\u6570\u5e73\u65b9\u548c\u4e0e\u8fd9\u4e24\u6570\u79ef\u7684\u548c\u7684\u79ef\u3002\u4e5f\u53ef\u4ee5\u8bf4\uff0c\u4e24\u6570\u7acb\u65b9\u5dee\u7b49\u4e8e\u4e24\u6570\u5dee\u4e0e\u8fd9\u4e24\u6570\u548c\u7684\u4e0d\u5b8c\u5168\u5e73\u65b9\u7684\u79ef \u3002
\u53c2\u8003\u8d44\u6599\uff1a\u767e\u5ea6\u767e\u79d1_\u7acb\u65b9\u5dee\u516c\u5f0f

平方和公式n(n+1)(2n+1)/6 即1^2+2^2+3^2+…+n^2=n(n+1)(2n+1)/6 (注:N^2=N的平方) 证明1+4+9+…+n^2=N(N+1)(2N+1)/6 证法一(归纳猜想法): 1、N=1时,1=1(1+1)(2×1+1)/6=1 2、N=2时,1+4=2(2+1)(2×2+1)/6=5 3、设N=x时,公式成立,即1+4+9+…+x2=x(x+1)(2x+1)/6 则当N=x+1时, 1+4+9+…+x2+(x+1)2=x(x+1)(2x+1)/6+(x+1)2 =(x+1)[2(x2)+x+6(x+1)]/6 =(x+1)[2(x2)+7x+6]/6 =(x+1)(2x+3)(x+2)/6 =(x+1)[(x+1)+1][2(x+1)+1]/6 也满足公式 4、综上所述,平方和公式1^2+2^2+3^2+…+n^2=n(n+1)(2n+1)/6成立,得证。 证法二(利用恒等式(n+1)^3=n^3+3n^2+3n+1): (n+1)^3-n^3=3n^2+3n+1, n^3-(n-1)^3=3(n-1)^2+3(n-1)+1 .............................. 3^3-2^3=3*(2^2)+3*2+1 2^3-1^3=3*(1^2)+3*1+1. 把这n个等式两端分别相加,得: (n+1)^3-1=3(1^2+2^2+3^2+....+n^2)+3(1+2+3+...+n)+n, 由于1+2+3+...+n=(n+1)n/2, 代人上式得: n^3+3n^2+3n=3(1^2+2^2+3^2+....+n^2)+3(n+1)n/2+n 整理后得: 1^2+2^2+3^2+....+n^2=n(n+1)(2n+1)/6

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