Show that a matrix is a multiple of the identity
40478
If $C$ commutes with certain matrices $A$ and $B$, why is $C$ a scalar multiple of the identity?
130799
Matrix of rank 1; show that $A^2=cA$ for some scalar $c$.
20331
Determinant of a $2\times 2$ block matrix
87441
Proof involving matrix equation
10083
Determinant of matrix times a constant.
137920
Proving an equation with invertible matrices
101040
Prove the equality: $\det\left[\begin{smallmatrix} -2a &a+b &a+c \\ b+a&-2b &b+c \\ c+a&c+b &-2c \end{smallmatrix}\right] = 4(a+b)(b+c)(c+a)$
19203
Is the rank of a matrix the same of its transpose? If yes, how can I prove it?
97733
Can it be determined that the sum of the diagonal entries, of matrix A, equals the sum of eigenvalues of A
60598
Matrix $A^T A$ as sum of outer products
4517
Showing a $2\times2$ matrix is invertible
124827
Show that $Y\sim N(a+A\mu,AVA^T)$
13948
Matrix in a matrix
109312
How is the matrix identity $\det\begin{pmatrix}A&B\\B&A\end{pmatrix}=\det(A+B)\det(A-B)$ proved?
32103
Show that for a $2\times 2$ matrix $A^2=0$
44898
Help with commutative property of matrices problem
77554
Inverse of the sum of matrices