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Thailand Contests
Thailand National Olympiad
2012 Thailand Mathematical Olympiad
7
7
Part of
2012 Thailand Mathematical Olympiad
Problems
(1)
5 | m - n^2 if gcd (a, b) = 1 and 5 | ma^2 + b^2
Source: Thailand Mathematical Olympiad 2012 p7
8/17/2020
Let
a
,
b
,
m
a, b, m
a
,
b
,
m
be integers such that gcd
(
a
,
b
)
=
1
(a, b) = 1
(
a
,
b
)
=
1
and
5
∣
m
a
2
+
b
2
5 | ma^2 + b^2
5∣
m
a
2
+
b
2
. Show that there exists an integer
n
n
n
such that
5
∣
m
−
n
2
5 | m - n^2
5∣
m
−
n
2
.
number theory
greatest common divisor
GCD
divides