MathDB
Problems
Contests
National and Regional Contests
India Contests
India National Olympiad
2019 India National OIympiad
3
INMO 2019 P3
INMO 2019 P3
Source:
January 20, 2019
number theory
Problem Statement
Let
m
,
n
m,n
m
,
n
be distinct positive integers. Prove that
g
c
d
(
m
,
n
)
+
g
c
d
(
m
+
1
,
n
+
1
)
+
g
c
d
(
m
+
2
,
n
+
2
)
≤
2
∣
m
−
n
∣
+
1.
gcd(m,n) + gcd(m+1,n+1) + gcd(m+2,n+2) \le 2|m-n| + 1.
g
c
d
(
m
,
n
)
+
g
c
d
(
m
+
1
,
n
+
1
)
+
g
c
d
(
m
+
2
,
n
+
2
)
≤
2∣
m
−
n
∣
+
1.
Further, determine when equality holds.
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