Consider $X = \{(x_1,x_2 \dots x_n) | x_i \geq 0\}$, a subset of $R^n$. Is $A(X)$ a closed set when $A$ is a linear map from X to $R^m$?
140225
Linear transformation maps the first quadrant to a closed set
99236
Interior of closure of an open set
12293
Let X be a T1 space, and show that X is normal if and only if each neighbourhood of a closed set F contains the closure of some neighbourhood of F
35573
A closed ball in a metric space is a closed set
121304
Is the set of polynomials of degree less than or equal to $n$ closed?
11114
Is a closed subset of a compact set (which is a subset of a metric space $M$) compact?
111538
If $S \subseteq X$ is closed, is $f(S,r)$ necessarily closed?
15645
Is convex open set in $\mathbb{R}^n$ is regular?
148994
$K \subset \mathbb{R}^n$ is compact iff it is closed and bounded
125962
The set $A'$ is closed in a $T_1$ space
80827
Let $A$ be a nonempty subset of $\mathbb{R}$. Prove...
143105
Show that, for every real number a, the set {$x ∈ S | f(x) ≤ a$} is a closed subset of $\mathbb R^d$
108740
$C^1[a,b]$ is closed in $C[a,b]$
41611
Open and closed set in n by n matrices space.
115376
Is $(-\infty,3]\cap(0,1)^c\cap[-1,\infty)$ closed? Open? What are interior points?
106944
Is the set defined by y=sin(1/x) open or closed?
143586
Is $[0,1]$ a union of family of disjoint closed intervals?