1. Consider the functions f : A → B and g : B → C. a. If f and g are both injective, show that so is go f. b. Suppose that gof is injective. Are f and g necessarily injective? Prove or provide a counterexample. c. If f and g are both surjective, show that so is g o f. d. Suppose that gof is surjective. Are f and g necessarily surjective? Prove or provide a counterex- ample.

Elements Of Modern Algebra
8th Edition
ISBN:9781285463230
Author:Gilbert, Linda, Jimmie
Publisher:Gilbert, Linda, Jimmie
Chapter1: Fundamentals
Section1.2: Mappings
Problem 10E: For each of the following parts, give an example of a mapping from E to E that satisfies the given...
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Answer a and b

1. Consider the functions f : A → B and g : B → C.
a. If f and g are both injective, show that so is go f.
b. Suppose that gof is injective. Are f and g necessarily injective? Prove or provide a counterexample.
c. If f and g are both surjective, show that so is g o f.
d. Suppose that gof is surjective. Are f and g necessarily surjective? Prove or provide a counterex-
ample.
Transcribed Image Text:1. Consider the functions f : A → B and g : B → C. a. If f and g are both injective, show that so is go f. b. Suppose that gof is injective. Are f and g necessarily injective? Prove or provide a counterexample. c. If f and g are both surjective, show that so is g o f. d. Suppose that gof is surjective. Are f and g necessarily surjective? Prove or provide a counterex- ample.
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