问题:已知集合A={a_1,a_2,a_3},集合B={b_1,b_2,b_3,b_4,b_5},可以建立从集合A到集合B的不同映射的个数是____.解析1:(分步乘法计数原理)问题可分为三步:第一步是集合A中的元素a_1对应集合B中的每一个元素,有5种不同的情况;第二步是集合A中的元素a_2对应集合B中的每一个元素,也有5种不同的情况;第三步是集合A中的元素a_3对应集合B中的每一个元素,也有5种不同的情况,根据分步乘法计数原理,从 Problem: The known set A = {a_1, a_2, a_3}, set B = {b_1, b_2, b_3, b_4, b_5}, the number of different mappings that can be established from set A to set B is ____. : (Step-by-step multiplication counting principle) The problem can be divided into three steps: The first step is to set the element a_1 in set A for each element in set B, there are five different situations; the second step is to set the elements in A a_2 corresponds to each element in set B, and there are 5 different cases. The third step is that element a_3 in set A corresponds to each element in set B, and there are 5 different cases. According to the principle of stepwise multiplication counting, From