If $A, B, C$ are three $n \times n$ matrices,then $(ABC)' = $

Assuming that the sums and products given below are defined,which of the following is not true for matrices?

Matrix theory was introduced by

Let $P$ be the set of all non-singular matrices of order $3$ over $\mathbb{R}$ and $Q$ be the set of all orthogonal matrices of order $3$ over $\mathbb{R}$. Then,

Construct a $3 \times 4$ matrix,whose elements are given by $a_{i j}=\frac{1}{2}|-3 i+j|$.

If $A = \frac{1}{\pi} \begin{bmatrix} \sin^{-1}(x\pi) & \tan^{-1}(\frac{x}{\pi}) \\ \sin^{-1}(\frac{x}{\pi}) & \cot^{-1}(\pi x) \end{bmatrix}$ and $B = \begin{bmatrix} -\frac{1}{\pi} \cos^{-1}(x\pi) & \frac{1}{\pi} \tan^{-1}(\frac{x}{\pi}) \\ \frac{1}{\pi} \sin^{-1}(\frac{x}{\pi}) & -\frac{1}{\pi} \tan^{-1}(\pi x) \end{bmatrix}$,then $A-B$ is equal to: