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National and Regional Contests
PEN Problems
PEN P Problems
24
24
Part of
PEN P Problems
Problems
(1)
P 24
Source:
5/25/2007
Show that any integer can be expressed as the form
a
2
+
b
2
−
c
2
a^{2}+b^{2}-c^{2}
a
2
+
b
2
−
c
2
, where
a
,
b
,
c
∈
Z
a, b, c \in \mathbb{Z}
a
,
b
,
c
∈
Z
.
Additive Number Theory