MHT CET · Maths · Matrices
The matrix \(A=\left[\begin{array}{ccc}a & -1 & 4 \\ -3 & 0 & 1 \\ -1 & 1 & 2\end{array}\right]\) is not invertible only if a =
- A -17
- B -16
- C 16
- D 17
Answer & Solution
Correct Answer
(A) -17
Step-by-step Solution
Detailed explanation
(D)
Since \(\mathrm{A}\) is not invertible, \(|\mathrm{A}|=0\)
\(\begin{aligned} \therefore &\left|\begin{array}{ccc}a & -1 & 4 \\ -3 & 0 & 1 \\ -1 & 1 & 2\end{array}\right|=0\end{aligned}\)
\(\mathrm{a}(0-1)-(-1)(-6+1)+4(-3-0)=0 \Rightarrow-\mathrm{a}\) \(-5-12=0 \Rightarrow \mathrm{a}=-17\)
Since \(\mathrm{A}\) is not invertible, \(|\mathrm{A}|=0\)
\(\begin{aligned} \therefore &\left|\begin{array}{ccc}a & -1 & 4 \\ -3 & 0 & 1 \\ -1 & 1 & 2\end{array}\right|=0\end{aligned}\)
\(\mathrm{a}(0-1)-(-1)(-6+1)+4(-3-0)=0 \Rightarrow-\mathrm{a}\) \(-5-12=0 \Rightarrow \mathrm{a}=-17\)
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