»º º
December 28, 2004
1 1
1
d a, b d | a, d | b d | am + bn,
m, n
1.1 x99y xy x, y x, y
10x + 9 90 + y = x
y ⇒ 9xy − 90x + 9y = 0
⇒ xy − 10x + y = 0
⇒ (x + 1)(y − 10) = −10.
x + 1 2 5 10
y − 10 −5 −2 −1 ⇒ (x, y) = (1, 5), (4, 8), (9, 9).
1.2 m, n
n3+ 1 mn − 1
m, n
(mn − 1) | (n3+ 1), (mn − 1) | (mn − 1)
(mn − 1) | (n3+ 1)m − (mn − 1)n2 = n2+ m,
(mn − 1) | (n3+ 1)m3− (mn − 1)(m2n2+ mn + 1) = m3+ 1.
n3+ 1
mn − 1,m3+ 1
mn − 1,n2+ m mn − 1
m, n m ≥ n ≥ 1 m, n
1 m ≤ 2(mn − 1) n2 ≤ mn ≤ 2(mn − 1) n2+ m
mn − 1 = 1, 2, 3, 4.
(1)
n2+ m mn − 1 = 1,
(n − 1)(m − n − 1) = 2 (m, n) = (5, 2), (5, 3) (2)
n2+ m mn − 1 = 2,
(2n − 1)(4m − 2n − 1) = 9 (m, n) = (2, 2), (3, 1)
(3)
n2+ m mn − 1 = 3,
(3n − 1)(9m − 3n − 1) = 28 (m, n) = (2, 1) (4)
n2+ m mn − 1 = 4,
(m, n)
(m, n) = (2, 5), (3, 5), (1, 3), (1, 2).
(m, n) = (5, 2), (2, 5), (5, 3), (3, 5), (2, 2), (3, 1), (1, 3), (2, 1), (1, 2)
1.1 ABC 15 P BC P A, P B, P C P A
1.2 x66y xy x, y x, y
1.3 x9999y xy x, y x, y
1.4
x2− y2 = 611
x, y
1.5
(m2+ n)(m + n2) = (m + n)3
m, n
7 4 4
p
2p−1− 1 p
p
- DZ
p 4 1 x, y
x2− py2 = 4
p y - DZ