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National and Regional Contests
Korea Contests
Korea Junior Mathematics Olympiad
2018 Korea Junior Math Olympiad
6
6
Part of
2018 Korea Junior Math Olympiad
Problems
(1)
Minimize the sum of difference squares
Source: KJMO 2018 p6
7/26/2019
Let there be a figure with
9
9
9
disks and
11
11
11
edges, as shown below.We will write a real number in each and every disk. Then, for each edge, we will write the square of the difference between the two real numbers written in the two disks that the edge connects. We must write
0
0
0
in disk
A
A
A
, and
1
1
1
in disk
I
I
I
. Find the minimum sum of all real numbers written in
11
11
11
edges.
algebra