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Ireland Contests
Ireland National Math Olympiad
2010 Irish Math Olympiad
3
Inequality
Inequality
Source: 2010 IrMO Paper 1 Problem 3
January 30, 2018
inequalities
Problem Statement
Suppose
x
,
y
,
z
x,y,z
x
,
y
,
z
are positive numbers such that
x
+
y
+
z
=
1
x+y+z=1
x
+
y
+
z
=
1
. Prove that (a)
x
y
+
y
z
+
x
z
≥
9
x
y
z
xy+yz+xz\ge 9xyz
x
y
+
yz
+
x
z
≥
9
x
yz
; (b)
x
y
+
y
z
+
x
z
<
1
4
+
3
x
y
z
xy+yz+xz<\frac{1}{4}+3xyz
x
y
+
yz
+
x
z
<
4
1
+
3
x
yz
;
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