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National and Regional Contests
PEN Problems
PEN K Problems
27
27
Part of
PEN K Problems
Problems
(1)
K 27
Source:
5/25/2007
Find all functions
f
:
N
→
N
f: \mathbb{N}\to \mathbb{N}
f
:
N
→
N
such that for all
m
,
n
∈
N
m,n\in \mathbb{N}
m
,
n
∈
N
:
f
(
f
(
m
)
+
f
(
n
)
)
=
m
+
n
.
f(f(m)+f(n))=m+n.
f
(
f
(
m
)
+
f
(
n
))
=
m
+
n
.
function
induction
strong induction
Functional Equations