No $T\in\mathcal{K}(X,Y)$ is onto
44738
Compact operators on an infinite dimensional Banach space cannot be surjective
67796
How to prove that the algebra $k[x, xy, xy^2, xy^3, \dotsc]$ is not finitely generated?
135046
Can this quick way of showing that $K[X,Y]/(Y-X^2)\cong K[X]$ be turned into a valid argument?
70249
Irreducibility of Polynomials in $k[x,y]$
71725
$\mathcal N (A):=\mathcal P(A)\setminus\{\varnothing\}$ notation
106091
Showing $\mathcal{P}(X)$ is isomorphic to $2^X$
63453
A proof of the fact that the Fourier transform is not surjective from $\mathcal{L}^1(\mathbb{R})$ to $C_0( \mathbb{R})$
154612
$\int_{0}^{x} f(t) dt \ge {f(x)}$ holds or not on $[0,1]$
37813
If $T\colon \mathbb R^n \to \mathbb R^n $ linear and $T^2 = kT$
118903
The sup norm on $C[0,1]$ is not equivalent to another one, induced by some inner product
52596
A basis for $k(X)$ regarded as a vector space over $k$
152465
Find the intersection of all $T_2$ topologies on an infinite set $X$
44453
Prove that the normalisation of $A=k[X,Y]/(Y^2-X^2-X^3)$ is $k[t]$ where $t=Y/X$ (Reid, Exercise 4.5)
115272
Showing that projections $\mathbb{R}^2 \to \mathbb{R}$ are not closed
156443
if $x$ and $y$ commute with $[x y]$, then $[x y]$ is nilpotent
60655
$\ker T\subset \ker S\Rightarrow S=rT$ when $S$ and $T$ are linear functionals
90826
Constructing a subset not in $\mathcal{B}(\mathbb{R})$ explicitly