What is the definition of a commutative ring with unity? What are the properties of a commutative ring with unity? Does every group have a unique additive identity? Why or why not? -
![abstract algebra - If a ring R has unity, then every ideal $I$ in the matrix ring $R_n$ is of the form $A_n$ - Mathematics Stack Exchange abstract algebra - If a ring R has unity, then every ideal $I$ in the matrix ring $R_n$ is of the form $A_n$ - Mathematics Stack Exchange](https://i.stack.imgur.com/6L0X1.png)
abstract algebra - If a ring R has unity, then every ideal $I$ in the matrix ring $R_n$ is of the form $A_n$ - Mathematics Stack Exchange
![abstract algebra - Prove that $(\Bbb Z_n, +_n, \cdot_n)$ is a commutative ring with unity - Mathematics Stack Exchange abstract algebra - Prove that $(\Bbb Z_n, +_n, \cdot_n)$ is a commutative ring with unity - Mathematics Stack Exchange](https://i.stack.imgur.com/O9Yf9.jpg)