7.1 Basic Definitions and Examples
March 31, 2019
Definitions - ring, commutative ring, ring with identity, zero divisor, unit, subring
7.1.03
March 31, 2019
Let \(R\) be a ring with identity and let \(S\) be a subring of \(R\) containing the identity. Prove that if \(u\) is a unit in \(S\) then \(u\) is a unit in \(R\). Show by example that the converse is false.
7.1.05
March 31, 2019
Decide which of the following are subrings of \(\mathbb{Q}\)