Question

Which of the following function f: Z X Z → Z is not onto?

(a) f(a, b) = a + b

(b) f(a, b) = a

(c) f(a, b) = |b|

(d) f(a, b) = a – b

This question was posed to me during an online exam.

My question comes from Functions in division Basic Structures: Sets, Functions, Sequences, Sums and Matrices of Discrete Mathematics

Answer 1

Right choice is (c) f(a, b) = |b|

The best I can explain: The function is not onto as f(a)≠b.