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National and Regional Contests
Iran Contests
Iran MO (3rd Round)
2005 Iran MO (3rd Round)
4
P,Q
P,Q
Source: Iran 2005
August 27, 2005
function
ratio
algebra proposed
algebra
Problem Statement
Suppose
P
,
Q
∈
R
[
x
]
P,Q\in \mathbb R[x]
P
,
Q
∈
R
[
x
]
that
d
e
g
P
=
d
e
g
Q
deg\ P=deg\ Q
d
e
g
P
=
d
e
g
Q
and
P
Q
′
−
Q
P
′
PQ'-QP'
P
Q
′
−
Q
P
′
has no real root. Prove that for each
λ
∈
R
\lambda \in \mathbb R
λ
∈
R
number of real roots of
P
P
P
and
λ
P
+
(
1
−
λ
)
Q
\lambda P+(1-\lambda)Q
λ
P
+
(
1
−
λ
)
Q
are equal.
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