Question

Prove that it is impossible to have a group of nine people at a party such that each one knows exactly five of the others in the group.​

Answer 1

Answer:

"

Prove that it is impossible to have a group of nine people at a party such that each one knows exactly five of the others in the group.

Solution:

The graph of this problem has nine vertices, one for each member of the group attending the party. ... The sum of the degrees of the vertices is 9 × 5 = 45. "

Explanation:

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