等差数列前n项立方和公式-天气预报

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等差数列前n项立方和公式

更新时间： 2021-02-06 05:06:43

1、a(n)=a(1)+(n-1)d

2、[a(n)]^3=[a(1)+(n-1)d]^3=[a(1)]^3+3(n-1)d[a(1)]^2+3(n-1)^2d^2 a(1)+(n-1)^3d^3

3、[a[1]]^3+a[2]^3+...........+a[n]^3

4、=n[a(1)]^3

5、+3d[a(1)]^2 [0+1+2+.......(n-1)]

6、+3d^2 a(1) [0^2+1^2+...........+(n-1)^2]

7、+d^3 [0^3+1^3+........+(n-1)^3]

8、=n[a(1)]^3+3d[a[1]]^2 n(n-1)/2+ n[a(1)]^3*(n-1)n(2n-1)/2+d^3*n^2(n-1)^2/4

关键词：等差数列立方公式

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