Hi, I am new to algorithms and i have following assingment to do, although i understand Greedy algorithm but i have no idea how to proceed

please help me solve these questions

1. Prove that a graph with n nodes and more than n-1 edges must contain at least one cycle.

2. Suppose the cost of laying a telephone cable from point a to point b is proportional to the Euclidean distance from a to b. A certain number of towns are to be connected at minimum cost. Find an example where it costs less to lay are connected at minimum cost. Find an example where it costs less to lay the cables via an exchange situated in between the towns than to use only direct links.

Please help........