Question

已知集合P={a,b,c},Q={-1,0,1},映射f：P到Q中满足f（b）=0的映射个数共有?

Answer 1

①a→0,b→0,c→-1

②a→0,b→0,c→0

③a→0,b→0,c→1

④a→1,b→0,c→-1

⑤a→1,b→0,c→0

⑥a→1,b→0,c→1

⑦a→-1,b→0,c→-1

⑧a→-1,b→0,c→0

⑨a→-1,b→0,c→1

共9种