page1878 Rings Matthias Lorentzen...mattegrisenforlag.com
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Question
Given a homomorphism `phi : A rightarrow B`, we define an equivalence
relation ~ on A by:
`x ~ y Leftrightarrow phi(x) = phi(y)`.
Is it true that the equivalence class [x] of x
under this relation is:
[x] = x + ker (`phi`)
?
