Existence of a real $2 \times 2$ matrix M such that $M^2 = \begin{pmatrix} -1 & 0 \\ 0 & -1-\epsilon \end{pmatrix}$
62232
A real $2 \times 2 $ matrix $M$ such that $M^2 = \tiny \begin{pmatrix} -1&0 \\ 0&-1-\epsilon \\ \end{pmatrix}$ , then :
11620
Is it true that any matrix in $M_2(\mathbb R)$ is the sum of two squares?
148946
If $\mathbf{A}$ is a $2\times 2$ matrix that satisfies $\mathbf{A}^2 - 4\mathbf{A} - 7\mathbf{I} = \mathbf{0}$, then $\mathbf{A}$ is invertible
20331
Determinant of a $2\times 2$ block matrix
137081
Is the set of real matrices diagonalizable in $\mathcal M_n(C)$ dense in the set of all companion matrices?
73697
Let $A, B$ be $n\times n$ with $n\ge 2$ nonsingular matrices with real entries such that $A^{-1} + B^{-1} =(A+B)^{-1}$
139685
If $A^2$ and $B^2$ are similar matrices, do $A$ and $B$ have to be similar?
153961
Determinant of $2 \times 2$ block matrix with commuting blocks
11857
$A$ be a complex $3\times 3$ matrix such that $A^3=-I$
38550
2x2 matrices with sum of diagonal entries equal zero
98273
minimal polynomial of powers of a matrix
6323
existence of complex structure in dimension 2
108850
Complex matrix that commutes with another complex matrix.
87331
Real polynomial in two variables
58595
Existence of a G-invariant matrix
128760
If $A$ and $B$ two $n\times n$ matrix such that $AB=BA$, then $\dim(A\cap B)$?
99662
proving than every $2\times 2$ is similar to a united form