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2024-IMOC
N4
a,b,c in S then ab+c in S
a,b,c in S then ab+c in S
Source: 2024IMOC
August 1, 2024
number theory
Problem Statement
Given a set of integers
S
S
S
satisfies that: for any
a
,
b
,
c
∈
S
a,b,c\in S
a
,
b
,
c
∈
S
(
a
,
b
,
c
a,b,c
a
,
b
,
c
can be the same),
a
b
+
c
∈
S
ab+c\in S
ab
+
c
∈
S
\\ Find all pairs of integers
(
x
,
y
)
(x,y)
(
x
,
y
)
such that if
x
,
y
∈
S
x,y\in S
x
,
y
∈
S
, then
S
=
Z
S=\mathbb{Z}
S
=
Z
.
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