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Problems
Contests
International Contests
Baltic Way
1995 Baltic Way
6
6
Part of
1995 Baltic Way
Problems
(1)
Very old
Source: Baltic Way 1995
10/8/2011
Prove that for positive
a
,
b
,
c
,
d
a,b,c,d
a
,
b
,
c
,
d
a
+
c
a
+
b
+
b
+
d
b
+
c
+
c
+
a
c
+
d
+
d
+
b
d
+
a
≥
4
\frac{a+c}{a+b}+\frac{b+d}{b+c}+\frac{c+a}{c+d}+\frac{d+b}{d+a}\ge 4
a
+
b
a
+
c
+
b
+
c
b
+
d
+
c
+
d
c
+
a
+
d
+
a
d
+
b
≥
4
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inequalities proposed
inequalities