Fill in the eight vertices of a square with the eight numbers of - 1, - 2, - 3, - 4, - 5, - 6, - 7, - 8. Each vertex can only fill in one number, so that the sum of the four vertices on the six faces of the square is equal

Fill in the eight vertices of a square with the eight numbers of - 1, - 2, - 3, - 4, - 5, - 6, - 7, - 8. Each vertex can only fill in one number, so that the sum of the four vertices on the six faces of the square is equal

The square is - 18
Add - 8, - 3, - 6, - 1 clockwise from the left on the front and - 2. - 5, - 4, - 7 clockwise from the left on the back,
The sum of each side is - 18

Syndrome 2 / 1 * 4 / 3 * 6 / 5 * 8 / 7 *. (2n) / (2n-1) > √ (2n + 1)

2^2 > 1*3
4^2 > 3*5
.
(2n)^2 ＞ (2n-1)(2n+1)
∴(2*4*6*8*...2n)^2 ＞ 1*3^2*5^2*7^2*...(2n-1)^2*(2n+1)
∴[(2*4*6*8*...2n)/(1*3*5*7*...(2n-1))]^2 ＞ 2n+1
∴2/1*4/3*6/5*8/7*.(2n)/(2n-1) ＞ √(2n+1)

What is 1 / (1 × 3) + 1 / (3 × 5) + 1 / (5 × 7) +. + 1 / (2n-1) (2n + 1) equal to?

=1/2（1-1/3+1/3-1/5+…… +1/（2n-1）-1/（2n+1））
1/2（1-1/（2n+1））=n/2n+1