Solutions To Mathematics Textbooks/Proofs and Fundamentals/Chapter 4
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Exercise 4.1.1[edit | edit source]
(1), (3) and (6) are functions.
Exercise 4.1.2[edit | edit source]
The first one and the fourth one are functions (here I've assumed that "mother" and "father" were meant biologically, and that not everyone has precisely one person they'd call a "best friend").
Exercise 4.1.3[edit | edit source]
(i) and (iv) represent functions.
Exercise 4.1.4[edit | edit source]
(2) and (3) properly describe functions.