JEE Main 20209 JanuaryMorning Shift
- Exam
- JEE Main
- Year
- 2020
- Date
- 9 January
- Shift
- Morning Shift
- Subject
- Mathematics
- Chapter
- Matrices
JEE Main 2020 · 9 January · Morning Shift · Mathematics · Matrices
If A = [ cases 1 & 1 & 2 1 & 3 & 4 1 & - 1 & 3 cases ], B = adjA...
If A = \left[\begin{cases}1 & 1 & 2 \\ 1 & 3 & 4 \\ 1 & - 1 & 3\end{cases}\right], B = adjA and then is equal to
Options
- A
- B
- C
- D
Correct answer
A.
Step-by-step solution
\left|A\right| = \left|\begin{cases}1 & 1 & 2 \\ 1 & 3 & 4 \\ 1 & - 1 & 3\end{cases}\right| = \left(\left(9 + 4\right) - 1\left(3 - 4\right) + 2\left(- 1 - 3\right)\right) = 13 + 1 - 8 = 6
\left|adjB\right| = \left|adjadjA\right| = {\left|A\right|}^{{\left(n - 1\right)}^{2}} = {\left|A\right|}^{4} = {\left(36\right)}^{2}
\left|adjB\right| = \left|adjadjA\right| = {\left|A\right|}^{{\left(n - 1\right)}^{2}} = {\left|A\right|}^{4} = {\left(36\right)}^{2}