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International Mathematical Olympiad
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2000
›
Problem 2
Problem 2
Let
a
,
b
,
c
a,b,c
a
,
b
,
c
be positive real numbers with
a
b
c
=
1
abc=1
ab
c
=
1
. Prove that
(
a
−
1
+
1
b
)
(
b
−
1
+
1
c
)
(
c
−
1
+
1
a
)
≤
1
(a-1+\frac1b)(b-1+\frac1c)(c-1+\frac1a)\le 1
(
a
−
1
+
b
1
)
(
b
−
1
+
c
1
)
(
c
−
1
+
a
1
)
≤
1
.
Step 1 of 4: Parametrize abc=1
Previous step
Next step
a
=
x
/
y
,
b
=
y
/
z
,
c
=
z
/
x
.
a=x/y,\quad b=y/z,\quad c=z/x.
a
=
x
/
y
,
b
=
y
/
z
,
c
=
z
/
x
.
Detailed analysis
Positive x,y,z give every positive triple with product one.
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