Question:
Are the following set of ordered pairs functions? If so, examine whether the mapping is injective or surjective.
(i) {(x, y): x is a person, y is the mother of x}.
(ii){(a, b): a is a person, b is an ancestor of a}.
Solution:
(i) Given, {(x, y): x is a person, y is the mother of x}
It’s clearly seen that each person ‘x’ has only one biological mother.
Hence, the above set of ordered pairs make a function.
Now more than one person may have same mother. Thus, the function is many-many one and surjective.
(ii) Given, {(a, b): a is a person, b is an ancestor of a}
It’s clearly seen that any person ‘a’ has more than one ancestors.
Thus, it does not represent a function.