Show that for any graph $G$ if and for verticies $u,v$ in G then if $|N(u) \cap N(v)|=1 $ then Graph G is r regular. $N(u)$ means the neighborhood of u all the vertices which are adjacent to u.
r regular means that every vertex in graph G has the same number of neighbors. I am not sure how I would I show this. How to start this proof.