Subrings and invertible elements
7903
Prove that $B[x] \cap B[x^{-1}]$ is integral over $B$
64644
An $r\times r$ submatrix of independent rows and independent columns is invertible (Michael Artin's book).
17059
A ring element with a left inverse but no right inverse?
35222
Characterizing units in polynomial rings
45792
Rigorous proof that surjectivity implies injectivity for finite sets
145221
Ring isomorphism (polynomials in one variable)
112485
Allowing the zero element in a field to have an inverse
45523
Can the product of two non invertible elements in a ring be invertible?
95373
Additive set function on a semiring of sets
83255
Finding inverse in non-commutative ring
120557
Group of invertible elements of a ring has never order $5$
149856
Image of ring homomorphism is a subring
83115
A set of elements in a reduced unity ring
21610
The monoid of fractions associated with the submonoid of cancellable elements of a commutative monoid E
133083
Injectivity and surjectivity of a recursive function
80616
A ring with few invertible elements
42809
How can we show that $(I-A)$ is invertible?