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Putnam
1988 Putnam
A5
Putnam 1988 A5
Putnam 1988 A5
Source:
August 6, 2019
Putnam
Problem Statement
Prove that there exists a unique function
f
f
f
from the set
R
+
\mathrm{R}^+
R
+
of positive real numbers to
R
+
\mathrm{R}^+
R
+
such that
f
(
f
(
x
)
)
=
6
x
ā
f
(
x
)
f(f(x)) = 6x-f(x)
f
(
f
(
x
))
=
6
x
ā
f
(
x
)
and
f
(
x
)
>
0
f(x)>0
f
(
x
)
>
0
for all
x
>
0
x>0
x
>
0
.
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