下列集合中哪些能定义函数?若能,求出函数的定义域和值域. (1){〈a,1〉,〈b,2〉,〈b,3〉,〈c,1〉}; (2){〈a,b〉,〈b,c
下列集合中哪些能定义函数?若能,求出函数的定义域和值域.
(1){〈a,1〉,〈b,2〉,〈b,3〉,〈c,1〉};
(2){〈a,b〉,〈b,c〉,〈a,c〉};
(3){〈〈a,i〉,〈b,2〉〉,〈〈a,2〉,〈b,1〉〉};
(4){〈1,a〉,〈2,a〉,〈3,a〉};
(5){〈|x|,x〉|x∈R};
(6){〈x,|x|〉|x∈R}.