Construct a $3 \times 2$ matrix whose elements are given by $a_{ij} = \frac{1}{2}|i - 3j|$.
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → $A = \begin{bmatrix} 1 & 5/2 \\ 1/2 & 2 \\ 0 & 3/2 \end{bmatrix}$ ##
In general a $3 \times 2$ matrix is given by $A = \begin{bmatrix} a_{11} & a_{12} \\ a_{21} & a_{22} \\ a_{31} & a_{32} \end{bmatrix}$.
Now, $a_{ij} = \frac{1}{2}|i - 3j|, i = 1, 2, 3$ and $j = 1, 2$.
Therefore:
$a_{11} = \frac{1}{2}|1 - 3 \times 1| = 1$
$a_{12} = \frac{1}{2}|1 - 3 \times 2| = \frac{5}{2}$
$a_{21} = \frac{1}{2}|2 - 3 \times 1| = \frac{1}{2}$
$a_{22} = \frac{1}{2}|2 - 3 \times 2| = 2$
$a_{31} = \frac{1}{2}|3 - 3 \times 1| = 0$
$a_{32} = \frac{1}{2}|3 - 3 \times 2| = \frac{3}{2}$
Hence the required matrix is given by:
$A = \begin{bmatrix} 1 & 5/2 \\ 1/2 & 2 \\ 0 & 3/2 \end{bmatrix}$