设集合A={1,2,3},集合B={3,6,9},给定函数f={(1,3),(2,9),(3,6)},则逆函数f-1

设集合A={1,2,3},集合B={3,6,9},给定函数f={(1,3),(2,9),(3,6)},则逆函数f-1
【正确答案】:{(3,1),(9,2),(6,3)}