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Groups and FieldsSuperchallengeHomomorphisms and Isomorphisms

Homomorphisms and Isomorphisms · Superchallenge problem

Define φ:Z9×Z9→Z9×Z9\varphi: \mathbb Z_9 \times \mathbb Z_9 \to \mathbb Z_9 \times \mathbb Z_9 by φ(a,b)=(2a+b mod 9, a+2b mod 9)\varphi(a,b) = (2a+b \bmod 9,\ a+2b \bmod 9). How many elements does ker⁡φ\ker\varphi have?