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Mathematics
Mathematics
Problem
1. If
f
f
f
is a function satisfying
f
(
x
+
y
)
=
f
(
x
)
f
(
y
)
f(x+y)=f(x) f(y)
f
(
x
+
y
)
=
f
(
x
)
f
(
y
)
for all
x
,
y
∈
N
x, y \in \mathbf{N}
x
,
y
∈
N
such that
f
(
1
)
=
3
f(1)=3
f
(
1
)
=
3
and
∑
x
=
1
n
f
(
x
)
=
120
\sum_{x=1}^{n} f(x)=120
∑
x
=
1
n
f
(
x
)
=
120
, find the value of
n
n
n
.
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