MCQ
If $A = \left( {\begin{array}{*{20}{c}}
{\alpha  - 1}\\
0\\
0
\end{array}} \right),\,\,\,B = \left( {\begin{array}{*{20}{c}}
{\alpha  + 1}\\
0\\
0
\end{array}} \right)$ be two matrices, then $AB^T$ is a non-zero matrix for $\left| \alpha  \right|$ not equal to
  • A
    $2$
  • B
    $0$
  • $1$
  • D
    $3$

Answer

Correct option: C.
$1$
c
Let $A = \left( {\begin{array}{*{20}{c}}
{\alpha  - 1}\\
0\\
0
\end{array}} \right),B = \left( {\begin{array}{*{20}{c}}
{\alpha  + 1}\\
0\\
0
\end{array}} \right)$

be two matrices.

$A{B^T} = \left( {\begin{array}{*{20}{c}}
{\alpha  - 1}\\
0\\
0
\end{array}} \right)\left( {\begin{array}{*{20}{c}}
{\alpha  + 1}&0&0
\end{array}} \right)$

           $ = \left( {\begin{array}{*{20}{c}}
{{\alpha ^2} - 1}&0&0\\
0&0&0\\
0&0&0
\end{array}} \right)$

Thus, $A{B^T}$ is non-zero matrix for $\left| \alpha  \right| \ne 1$

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