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Moldova Team Selection Test
2023 Moldova Team Selection Test
2
NUMBER THORY
NUMBER THORY
Source:
March 5, 2017
number theory
Problem Statement
Let
a
,
b
,
c
a,b,c
a
,
b
,
c
be distinct positive integers and let
r
,
s
,
t
r,s,t
r
,
s
,
t
be positive integers such that:
a
b
+
1
=
r
2
,
a
c
+
1
=
s
2
,
b
c
+
1
=
t
2
ab+1=r^2,ac+1=s^2,bc+1=t^2
ab
+
1
=
r
2
,
a
c
+
1
=
s
2
,
b
c
+
1
=
t
2
Prove that it is not possible that all three fractions
r
t
s
,
r
s
t
,
s
t
r
\frac{rt}{s}, \frac{rs}{t}, \frac{st}{r}
s
r
t
,
t
rs
,
r
s
t
are integers.
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