Sunday, 13 July 2014

discrete mathematics - Inductively the number of edges for a connected graph

Claim: Every connected graph with n vertices has at least n1 edges.



Proof by induction:



P(n) = "Every connected graph with n vertices has at least n1 edges." n1



Base case: A graph with 1 vertex has 0 edges.




Inductive step:




  1. Remove a vertex with the lowest degree and all its edges from the connected graph with n+1 vertices.


  2. The resulting graph has n vertices. Apply the inductive hypothesis - this graph has at least n1 edges.


  3. When you add the removed vertex back, it must connect to at least 1 vertex in order for the overall graph to be connected.


  4. The graph now contains at least n1+1 or n edges





I'm new to graph theory, so I'm wondering if I completed this induction proof with the right steps. Any other methods or additions to this proof would also be appreciated. Thanks!

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