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National and Regional Contests
China Contests
China National Olympiad
2021 China National Olympiad
2
2
Part of
2021 China National Olympiad
Problems
(1)
m divides linear sum of sequences
Source: 2021 China Mathematical Olympiad P2
11/24/2020
Let
m
>
1
m>1
m
>
1
be an integer. Find the smallest positive integer
n
n
n
, such that for any integers
a
1
,
a
2
,
…
,
a
n
;
b
1
,
b
2
,
…
,
b
n
a_1,a_2,\ldots ,a_n; b_1,b_2,\ldots ,b_n
a
1
,
a
2
,
…
,
a
n
;
b
1
,
b
2
,
…
,
b
n
there exists integers
x
1
,
x
2
,
…
,
x
n
x_1,x_2,\ldots ,x_n
x
1
,
x
2
,
…
,
x
n
satisfying the following two conditions: i) There exists
i
∈
{
1
,
2
,
…
,
n
}
i\in \{1,2,\ldots ,n\}
i
∈
{
1
,
2
,
…
,
n
}
such that
x
i
x_i
x
i
and
m
m
m
are coprimeii)
∑
i
=
1
n
a
i
x
i
≡
∑
i
=
1
n
b
i
x
i
≡
0
(
m
o
d
m
)
\sum^n_{i=1} a_ix_i \equiv \sum^n_{i=1} b_ix_i \equiv 0 \pmod m
∑
i
=
1
n
a
i
x
i
≡
∑
i
=
1
n
b
i
x
i
≡
0
(
mod
m
)
number theory
China