Gujarati
Hindi
3 and 4 .Determinants and Matrices
medium

Which of the following is(are) $NOT$ the square of a $3 \times 3$ matrix with real entries ?

$[A]$ $\left[\begin{array}{ccc}1 & 0 & 0 \\ 0 & 1 & 0 \\ 0 & 0 & -1\end{array}\right]$

$[B]$ $\left[\begin{array}{ccc}-1 & 0 & 0 \\ 0 & -1 & 0 \\ 0 & 0 & -1\end{array}\right]$

$[C]$ $\left[\begin{array}{lll}1 & 0 & 0 \\ 0 & 1 & 0 \\ 0 & 0 & 1\end{array}\right]$

$[D]$ $\left[\begin{array}{ccc}1 & 0 & 0 \\ 0 & -1 & 0 \\ 0 & 0 & -1\end{array}\right]$

A

$A,B$

B

$A,C$

C

$A,D$

D

$A,B,C$

(IIT-2017)

Solution

$|\mathrm{A}|^2$ cannot be $-\mathrm{ve}$

$\Rightarrow  A$ and $B$ option cannot be square of matrix

$C$ option is $\left|\begin{array}{lll}1 & 0 & 0 \\ 0 & 1 & 0 \\ 0 & 0 & 1\end{array}\right|^2$

$D$ option is $\left|\begin{array}{ccc}1 & 0 & 0 \\ 0 & 0 & 1 \\ 0 & -1 & 0\end{array}\right|^2$

Standard 12
Mathematics

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