Adjacency Matrix Paths
1. **Problem Statement:** Given an adjacency matrix of a graph, our tasks are:
a) Verify the given parts about the graph.
b) For each pair of vertices, determine how many paths of length 3 join them.
c) List all the 3-cycles in the graph, considering different permutations of the cycle as distinct.
2. **Understanding the adjacency matrix:**
The adjacency matrix $A$ of a graph with $n$ vertices is an $n \times n$ matrix where the element $A_{ij}$ is 1 if there is an edge from vertex $i$ to vertex $j$, and 0 otherwise.
3. **Paths of length 3 between vertices:**
The number of paths of length 3 from vertex $i$ to vertex $j$ is given by the entry $(i,j)$ in the matrix $A^3$, where $A^3 = A \times A \times A$.
To find $A^3$, multiply the adjacency matrix $A$ by itself three times.
4. **Finding 3-cycles:**
A 3-cycle is a cycle of length 3, i.e., vertices $a$, $b$, and $c$ where $a$ is connected to $b$, $b$ to $c$, and $c$ back to $a$.
Use the adjacency matrix to check for these triples: for vertices $i$, $j$, $k$, if $A_{ij} = 1$, $A_{jk} = 1$, and $A_{ki} = 1$, then $(i,j,k)$ forms a 3-cycle.
Since different permutations count separately, count all ordered triples that satisfy this.
5. **Summary:**
- Calculate $A^3$ to find the number of paths length 3 between all pairs.
- Identify all ordered triples $(i,j,k)$ where the above holds to enumerate different 3-cycles.
*Note:* Without the explicit adjacency matrix, numerical answers cannot be computed here. Use the above method with the given matrices to proceed.