discrete math please help 17 plz 16 In a group of 4 people i

16.) In a group of 4 people, is it possible for each person to have exactly 3 friends? Why? (Assume friendship is a symmetric relationship) If G is a simple graph with 15 edges and G? has 13 edges, how many vertices does G have

Solution

Lets Assume there are 4 friends A,B,C,D

A can have B,C,D as his friends

B can have A,C,D as his friends

C can have A,B,D as his friends

D can have A,B,C as his friends

When n people are there each person can have maximum n-1 friends.

In this case there are 4 people are so everybody can have max 3 friends.