MathCastle
Groups and FieldsSuperchallengeHomomorphisms and Isomorphisms

Homomorphisms and Isomorphisms · Superchallenge problem

Define φ:Z12×Z12→Z12×Z12\varphi: \mathbb Z_{12} \times \mathbb Z_{12} \to \mathbb Z_{12} \times \mathbb Z_{12} by φ(a,b)=(3a+b mod 12, a+3b mod 12)\varphi(a,b) = (3a+b \bmod 12,\ a+3b \bmod 12). How many elements does ker⁡φ\ker\varphi have?