Three out of seven × [] = 9 × [] = four out of five △ [] = a × [] 0

Three out of seven × [] = 9 × [] = four out of five △ [] = a × [] 0

3 / 7 × [7] = 9 × [1 / 3] = 4 / 5 ÷ [4 / 15] = a × [3] = 3
A=1

In the numbers 0,2.9, - 5, - 3.7,16, () is a natural number, () is an integer
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Among the numbers 0,2.9,4 / 5, - 5, - 3.7,16, (0,2,9,16) are natural numbers and (0,2,9, - 5,16) are integers

Known inequality: 1 / N + 1 + 1 / N + 2 + +1 / N + n > 1 / 12 ㏒ a (A-1) + 2 / 3 holds for all natural numbers n greater than 1, and the value range of real number a is obtained
In 1 / 12 ㏒ a (A-1), a is the base and (A-1) is the logarithm

Consider f (n) = 1 / (n + 1) + 1 / (n + 2) + +1 / (n + n), then f (n + 1) - f (n) = 1 / (2n + 1) + 1 / (2n + 2) - 1 / (n + 1) = 1 / (2n + 2) (2n + 1) > 0, then f (n) MIM = f (2) = 7 / 12, then 7 / 12 ＞ 1 / 12log [a] (A-1) + 2 / 3, log [a] (A-1) ＜ - 1. When 0 ＜ a ＜ 1, the inequality A-1 ＞ 1 / A is solved