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2015 IMO Shortlist
N2
Factorials divide
Factorials divide
Source: 2015 ISL N2
July 7, 2016
factorial
number theory
IMO Shortlist
Divisibility
Problem Statement
Let
a
a
a
and
b
b
b
be positive integers such that
a
!
+
b
!
a! + b!
a
!
+
b
!
divides
a
!
b
!
a!b!
a
!
b
!
. Prove that
3
a
≥
2
b
+
2
3a \ge 2b + 2
3
a
≥
2
b
+
2
.
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