A certain connected graph has 68 vertices and 72 edges. Does it have a circuit? Explain.

A connected graph that has no circuits or cycles is called a tree. In order for a connected graph to be a tree, it must have (n-1) edges where n is the number of vertices.

In this case, this connected graph has 68 vertices and 72 edges instead of just 67 edges which means that it does not qualify as a tree. So, if this connected does not qualify as tree, then it could have circuit or cycle.
By looking at the number of vertices and the number of edges, we can tell that this connected graph can have circuit because it has 4 more edges than vertices.

Well, it certainly sounds like this graph is hooked up pretty well with all those edges. If there's a path from one vertex to another, it's likely there's a path back, too. So, yes, I think this graph might just have a circuit hiding in there. But be careful, try not to trip over any edges!

To determine if a certain connected graph has a circuit, we can use the formula known as Euler's Formula:

Euler's Formula: V - E + F = 2

Where:
V represents the number of vertices in the graph.
E represents the number of edges in the graph.
F represents the number of faces in the graph.

In a connected graph, the number of faces is always 1, since it is not possible to have a disconnected face. Therefore, we can rewrite Euler's formula as:

V - E + 1 = 2

Now let's substitute the given values into the formula:

68 - 72 + 1 = 2

Simplifying this equation, we get:

-3 = 2

Since this equation is not true, it means that the given graph does not satisfy Euler's formula and therefore does not have a circuit.

To determine if a certain connected graph has a circuit, we first need to understand the concept of a circuit in graph theory.

A circuit is a path in a graph where the starting and ending vertices are the same, and no edges are repeated except for the starting and ending vertex. In other words, a circuit is a closed path with no repeated edges (except for the starting and ending edge).

Now, let's analyze the given information. We are told that the graph has 68 vertices and 72 edges. Since the graph is connected, it means that there is a path between every pair of vertices.

To determine if it has a circuit, we can apply a concept called Euler's formula. Euler's formula states that in any connected graph, the number of edges (E), vertices (V), and faces (F) are related by the equation:

E - V + F = 2

In this case, we have 68 vertices (V) and 72 edges (E). So, we can substitute these values into Euler's formula:

72 - 68 + F = 2

Simplifying this equation, we get:

4 + F = 2

Subtracting 2 from both sides:

F = 2 - 4

F = -2

This result tells us that the graph has -2 faces, which doesn't make sense since the number of faces cannot be negative.

Therefore, based on Euler's formula, we can conclude that the given graph cannot have a circuit.