jee-advanced 2019 Q6

jee-advanced · India · paper1 3x3 Matrices Determinant of Parametric or Structured Matrix
Let $$M = \left[ \begin{array} { l l l } 0 & 1 & a \\ 1 & 2 & 3 \\ 3 & b & 1 \end{array} \right] \quad \text { and } \quad \operatorname { adj } M = \left[ \begin{array} { r r r } - 1 & 1 & - 1 \\ 8 & - 6 & 2 \\ - 5 & 3 & - 1 \end{array} \right]$$ where $a$ and $b$ are real numbers. Which of the following options is/are correct?
(A) $a + b = 3$
(B) $\quad ( \operatorname { adj } M ) ^ { - 1 } + \operatorname { adj } M ^ { - 1 } = - M$
(C) $\operatorname { det } \left( \operatorname { adj } M ^ { 2 } \right) = 81$
(D) If $M \left[ \begin{array} { l } \alpha \\ \beta \\ \gamma \end{array} \right] = \left[ \begin{array} { l } 1 \\ 2 \\ 3 \end{array} \right]$, then $\alpha - \beta + \gamma = 3$
Let
$$M = \left[ \begin{array} { l l l } 
0 & 1 & a \\
1 & 2 & 3 \\
3 & b & 1
\end{array} \right] \quad \text { and } \quad \operatorname { adj } M = \left[ \begin{array} { r r r } 
- 1 & 1 & - 1 \\
8 & - 6 & 2 \\
- 5 & 3 & - 1
\end{array} \right]$$
where $a$ and $b$ are real numbers. Which of the following options is/are correct?\\
(A) $a + b = 3$\\
(B) $\quad ( \operatorname { adj } M ) ^ { - 1 } + \operatorname { adj } M ^ { - 1 } = - M$\\
(C) $\operatorname { det } \left( \operatorname { adj } M ^ { 2 } \right) = 81$\\
(D) If $M \left[ \begin{array} { l } \alpha \\ \beta \\ \gamma \end{array} \right] = \left[ \begin{array} { l } 1 \\ 2 \\ 3 \end{array} \right]$, then $\alpha - \beta + \gamma = 3$