For example, a geometry surrounded by multiple planes is called a polyhedron. If the number of faces of a polyhedron is f, the number of vertices is v and the number of edges is e, A: f=6, e= 12, v=8, f+v-e = 2; B: f=6，e= 10，v=6，F+V-E = 2； Law: number of vertices+number of faces-number of edges =2.
Knowledge points involved: list the number of faces, vertices and edges of geometry and calculate them directly; Let the number of faces of this polyhedron be x, and according to the number of vertices+number of faces-number of edges =2, the equation can be listed and solved.
The relationship among vertices, faces and edges is that in convex polyhedron, the number of vertices-number of edges+number of faces =2.
This relationship is also called polyhedral euler theorem. In number theory, euler theorem (also called Fermat-euler theorem or Euler function theorem) is about the property of congruence. Euler theorem is named after Swiss mathematician leonhard euler, and this theorem is considered as one of the most beautiful theorems in mathematics. Euler theorem is actually a generalization of Fermat's theorem.
A single polyhedron is a polyhedron whose surface can become spherical after continuous deformation.