✔ 最佳答案
數列一
0, 6, 24, 60, 120, ...
留意:
0 = 0 × 1 × 2 = 1 - 1 = 1³ - 1
6 = 1 × 2 × 3 = 8 - 2 = 2³ - 2
24 = 2 × 3 × 4 = 27 - 3 = 3³ - 3
60 = 3 × 4 × 5 = 64 - 4 = 4³ - 4
120 = 4 × 5 × 6 = 125 - 5 = 5³ - 5
因此,可以推測下一項是 5 × 6 × 7 = 210,
再下一項是 6 × 7 × 8 = 336。
也很易看出通項 (general term) 是 (n-1)n(n+1) = n³ - n
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數列二
6, 24, 60, 120, 210, ...
留意:
6 = 1 × 2 × 3
24 = 2 × 3 × 4
60 = 3 × 4 × 5
120 = 4 × 5 × 6
210 = 5 × 6 × 7
因此,可以推測下一項是 6 × 7 × 8 = 336,
再下一項是 7 × 8 × 9 = 504。
也很易看出通項 (general term) 是 n(n+1)(n+2) = n³ + 3n² + 2n
2014-02-08 23:35:20 補充:
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