Balmer, a Swiss middle school teacher, found the rule from spectral data 5 / 9, 12 / 16, 21 / 25, 32 / 36. Please write the seventh data ()

The general term is (n & # 178; - 4) / N & # 178;, n & # 8321; = 3, so the seventh number is n = 9, (n & # 178; - 4) / N & # 178; = (9 & # 178; - 4) / 9 & # 178; = 77 / 81

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1. Balmer, a Swiss middle school teacher, found the rule from the spectral data 5 / 9, 12 / 16, 21 / 25, 32 / 36. Please write the number n according to the rule
2. Balmer, a Swiss middle school teacher, found the rule from the spectral data 5 / 9, 12 / 16, 21 / 25, 32 / 36. Please write the seventh number according to the rule
3. A set of data: 9 / 5, 16 / 12, 25 / 21, 36 / 32. What's the seventh number
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