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Problems
Contests
National and Regional Contests
China Contests
XES Mathematics Olympiad
the 13th XMO
P2
Nice Algebra
Nice Algebra
Source:
September 16, 2023
algebra
Problem Statement
Given
n
∈
N
+
,
n
≥
3
,
a
1
,
a
2
,
⋯
,
a
n
∈
R
+
.
n\in\mathbb N_+,n\ge 3,a_1,a_2,\cdots ,a_n\in\mathbb R_+.
n
∈
N
+
,
n
≥
3
,
a
1
,
a
2
,
⋯
,
a
n
∈
R
+
.
Let
b
1
,
b
2
,
⋯
,
b
n
∈
R
+
b_1,b_2,\cdots ,b_n\in\mathbb R_+
b
1
,
b
2
,
⋯
,
b
n
∈
R
+
satisfy that for
∀
k
∈
{
1
,
2
,
⋯
,
n
}
,
\forall k\in\{1,2,\cdots ,n\},
∀
k
∈
{
1
,
2
,
⋯
,
n
}
,
∑
i
,
j
∈
{
1
,
2
,
⋯
,
n
}
\
{
k
}
i
≠
j
a
i
b
j
=
0.
\sum_{\substack{i,j\in\{1,2,\cdots ,n\}\backslash \{k\}\\i\neq j}}a_ib_j=0.
i
,
j
∈
{
1
,
2
,
⋯
,
n
}
\
{
k
}
i
=
j
∑
a
i
b
j
=
0.
Prove that
b
1
=
b
2
=
⋯
=
b
n
=
0.
b_1=b_2=\cdots =b_n=0.
b
1
=
b
2
=
⋯
=
b
n
=
0.
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