Question

Construct a $3\times 4$ matrix $A=\left[a_{ij}\right]$, whose element $a_{ij}$ is $a_{ij}=i-j$.

Answer 1

$A=\left[\begin{array}{cccc}{a}_{11}& a_{12}& a_{13}& a_{14}\\ a_{21}& a_{22}& a_{23}& a_{24}\\ a_{31}& a_{32}& a_{33}& a_{34}\end{array}\right]$

$\therefore A=\left[\begin{array}{cccc}0& -1& -2& -3\\ 1& 0& -1& -2\\ 2& 1& 0& -1\end{array}\right]$