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MathNet 2011 Question 35

Math Olympiad Vault · MathNet 2011

Question 35

Let $G$ be the set of matrices
$$
\begin{pmatrix} a & b \\ \hat{0} & \hat{1} \end{pmatrix}, \quad a, b \in \mathbb{Z}_7, a \neq \hat{0}.
$$

a) Show that $G$ is a group with respect to the matrix multiplication.
b) Prove that there exists no proper homomorphism from $G$ to $\mathbb{Z}_7$.