在解决某些涉及自然数n的概率问题时,如果能从问题的背景中探究出概率问题的递推关系,往往可以起到事半功倍的效果.下面通过几个例子加以说明.例1在正四面体的一个顶点处,有一只蚂蚁每一次都以13的概率从一个顶点爬到另一个顶点.(1)求它爬行了2、3、4次又分别回到起点的概率;(2 When solving certain probabilistic problems involving the natural number n, if we can explore the recurrence relations of the probabilistic problem from the background of the problem, we can often achieve a multiplier effect. Here are some examples to illustrate. Example 1 In the regular tetrahedron At one of the vertices, there is an ant that climbs from one vertex to another with a probability of 13 each time. (1) Find the probability that it crawls back to the starting point 2, 3, 4 times, respectively; (2)