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# D1 question... watch

1. how many trees are there that have 5 vertices and 4 edges :s

Probably pretty simple but how do i work this out, they can be drawn any number of ways surely x
2. (Original post by irish_4_life)
how many trees are there that have 5 vertices and 4 edges :s

Probably pretty simple but how do i work this out, they can be drawn any number of ways surely x
Here's a systematic method (a bit over kill, but....). I have assumed that the labelling on the vertices is not relevant.

Start by drawing all the trees with just one edge.

For each tree, add another edge in as many different ways as possible creating as many different trees with the extra edge; ignoring duplicates created.

Repeat previous step until you have 4 edges.

By my reckoning there are only
Spoiler:
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4
of them.

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