- Home
- Standard 12
- Mathematics
Construct a $3 \times 2$ matrix whose elements are given by $a_{i j}=\frac{1}{2}|i-3 j|$.
$A\, = \,\left[ {\begin{array}{*{20}{c}}
1&{\frac{3}{2}} \\
{\frac{1}{2}}&2 \\
0&{\frac{3}{2}}
\end{array}} \right]$
$A\, = \,\left[ {\begin{array}{*{20}{c}}
1&{\frac{5}{2}} \\
{\frac{1}{2}}&2 \\
0&{\frac{1}{2}}
\end{array}} \right]$
$A\, = \,\left[ {\begin{array}{*{20}{c}}
1&{\frac{5}{2}} \\
{\frac{1}{2}}&2 \\
0&{\frac{3}{2}}
\end{array}} \right]$
$A\, = \,\left[ {\begin{array}{*{20}{c}}
1&{\frac{5}{2}} \\
{\frac{1}{2}}&2 \\
0&{\frac{5}{2}}
\end{array}} \right]$
Solution
In general a $3 \times 2$ matrix is given by $A\, = \,\left[ {\begin{array}{*{20}{c}}
{{a_{11}}}&{{a_{12}}} \\
{{a_{21}}}&{{a_{22}}} \\
{{a_{31}}}&{{a_{32}}}
\end{array}} \right]$
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 $A\, = \,\left[ {\begin{array}{*{20}{c}}
1&{\frac{5}{2}} \\
{\frac{1}{2}}&2 \\
0&{\frac{3}{2}}
\end{array}} \right]$