Needs a counterexample for homomorphisms

In summary, the conversation discusses the concept of homomorphisms between groups and the existence of a well-defined homomorphism g in a specific scenario. The task is to find an example where f is injective but g is not. The person is struggling to come up with an example and is seeking help.
  • #1
playa007
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Homework Statement


Let A, B be groups and A' and B' be normal subgroups of A and B respectively. Let f: A --> B be a homomorphism with f(A') being a subgroup of B'. There is a well-defined homomorphism g: A/A' -----> B/B' defined by g: aA' ---> f(a)B'

Find an example in which f is injective, but g is not injective.

Homework Equations


I've proven that g is a well-defined homomorphism and that if f is surjective, then g is surjective.


The Attempt at a Solution

 
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  • #2
I'm having a difficult time coming up with an example. I know that if f is injective, then g is injective, so I'm looking for an example in which f is injective, but g is not injective. Any help would be greatly appreciated.
 

1. What is a homomorphism?

A homomorphism is a mathematical function that preserves the structure and operations of a mathematical system. It maps elements from one mathematical system to another while preserving their properties.

2. Why do we need a counterexample for homomorphisms?

A counterexample for homomorphisms is used to show that a given function does not preserve the structure and operations of a mathematical system. It helps to identify when a function is not a valid homomorphism.

3. Can you provide an example of a counterexample for homomorphisms?

Yes, an example of a counterexample for homomorphisms is the function f(x) = x^2, which maps the integers to the non-negative integers. This function does not preserve the addition operation, as f(a + b) ≠ f(a) + f(b) for some values of a and b.

4. How do counterexamples for homomorphisms relate to real-world applications?

Counterexamples for homomorphisms are important in real-world applications, as they help to identify when a function is not a valid homomorphism and therefore cannot be used to model a real-world system. This ensures that the mathematical models used in real-world applications are accurate and reliable.

5. How can we use counterexamples for homomorphisms in problem-solving?

In problem-solving, counterexamples for homomorphisms can be used to identify and correct errors in mathematical models. By finding a counterexample, we can see where a function fails to preserve the structure and operations of a mathematical system, and then adjust the model accordingly.

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