怎么会这样呢?不至于吧

来源: 魁北克人 2015-06-27 10:39:45 [] [旧帖] [给我悄悄话] 本文已被阅读: 次 (465 bytes)
2.
|x(x-a)| = x(x-a) when x >=a
|x(x-a)| = x(a-x) when x < a

3.
Let b = a - 1. Then 0 < b < 1
a1 = a, a2 = a - 1 = b,
a3 = b - 1 = - (1-b), a4 = (1-b) - 1 = -b
a5 = b - 1 = - (1-b), a6 = (1-b) - 1 = -b
......

5.
(x - 2y)^2 + (y + 1)^2 = 1 + 4
There are a total of 8 defferent pairs of integer solutions by considering the signs and symmetries.
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