The determinant of a skew-symmetric matrix of order $3$ is always:

If $\left| \begin{array}{ccc} y + z & x & y \\ z + x & z & x \\ x + y & y & z \end{array} \right| = k(x + y + z)(x - z)^2$,then $k = $

If $|A|$ denotes the value of the determinant of the square matrix $A$ of order $3$,then $|-2A|=$

Let $a, b, c, d$ be in arithmetic progression with common difference $\lambda$. If
$\left|\begin{array}{lll} x+a-c & x+b & x+a \\ x-1 & x+c & x+b \\ x-b+d & x+d & x+c \end{array}\right|=2$
then the value of $\lambda^{2}$ is equal to $.....$

$\left| {\begin{array}{ccc} 1/a & a^2 & bc \\ 1/b & b^2 & ca \\ 1/c & c^2 & ab \end{array}} \right| = $

$\left|\begin{array}{ccc}a-b-c & 2a & 2a \\ 2b & b-c-a & 2b \\ 2c & 2c & c-a-b\end{array}\right|$ is equal to