数列(求数列的前N项和)
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求和:1×4 + 2×5 + 3×6 + ……+ n×(n +3)
![数列(求数列的前N项和)](/uploads/image/z/18372218-50-8.jpg?t=%E6%95%B0%E5%88%97%28%E6%B1%82%E6%95%B0%E5%88%97%E7%9A%84%E5%89%8DN%E9%A1%B9%E5%92%8C%29)
解题思路: 先分析通项 在利用拆项法 转化前N的自然数的平方和与前N个自然数的和
解题过程:
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最终答案:略
解题过程:
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最终答案:略