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IMO Shortlist
2009 IMO Shortlist
4
IMO Shortlist 2009 - Problem A4
IMO Shortlist 2009 - Problem A4
Source:
July 5, 2010
inequalities
IMO Shortlist
Problem Statement
Let
a
a
a
,
b
b
b
,
c
c
c
be positive real numbers such that
a
b
+
b
c
+
c
a
≤
3
a
b
c
ab+bc+ca\leq 3abc
ab
+
b
c
+
c
a
≤
3
ab
c
. Prove that
a
2
+
b
2
a
+
b
+
b
2
+
c
2
b
+
c
+
c
2
+
a
2
c
+
a
+
3
≤
2
(
a
+
b
+
b
+
c
+
c
+
a
)
\sqrt{\frac{a^2+b^2}{a+b}}+\sqrt{\frac{b^2+c^2}{b+c}}+\sqrt{\frac{c^2+a^2}{c+a}}+3\leq \sqrt{2}\left(\sqrt{a+b}+\sqrt{b+c}+\sqrt{c+a}\right)
a
+
b
a
2
+
b
2
+
b
+
c
b
2
+
c
2
+
c
+
a
c
2
+
a
2
+
3
≤
2
(
a
+
b
+
b
+
c
+
c
+
a
)
Proposed by Dzianis Pirshtuk, Belarus
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