Solving 3-1 Trees: Proving Even # of Vertices & Finding Leaf #s

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A 3-1 tree is defined by having vertices with degrees of either 3 or 1. It can be shown that such trees must contain an even number of vertices due to the properties of vertex degrees and edges. For trees with four or fewer vertices of degree 3, specific configurations can be drawn to illustrate their structure. Additionally, a formula can be derived to calculate the number of leaves in a 3-1 tree based on the total number of vertices, m. Understanding these characteristics is crucial for solving problems related to 3-1 trees.
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please help solve tree problem...

A tree is called a 3-1 tree if every vertex in the tress has degree equal to either 3 or 1.
1. Draw all 3-1 trees with four or fewer vertices of degree 3.
2. Prove that a 3-1 tree must have an even number of vertices.
3. Find a formula for the number of leaves in a 3-1 tree that has exactly m vertices.
 
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