InterviewSolution
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If \(\begin{bmatrix} 1 & -4 & 3 \\\ 0 & 6 & -7 \\\ 2 & 4 & λ \end{bmatrix}\) is not an invertible matrix, then what is the value of λ ? |
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Answer» Correct Answer - Option 3 : -8 Concept: If A is not an invertible matrix then |A| = 0 If A is a singular matrix then |A| = 0 Calculation: Given A = \(\begin{bmatrix} 1 & -4 & 3 \\\ 0 & 6 & -7 \\\ 2 & 4 & λ \end{bmatrix}\) is not an invertible matrix. ⇒ A is a singular matrix. ⇒ |A| = 0 ⇒ \(\begin{vmatrix} 1 & -4 & 3 \\\ 0 & 6 & -7 \\\ 2 & 4 & λ \end{vmatrix}\) = 0 ⇒ 1(\(\rm 6\lambda + 28 \)) + 4 (0 + 14) + 3 (0 - 12) = 0 ⇒ \(\rm 6\lambda + 28 + 56 - 36 = 0\) ⇒ \(\rm 6\lambda + 48 = 0\) ⇒ \(\rm \lambda = - 8\) Hence, if \(\begin{bmatrix} 1 & -4 & 3 \\\ 0 & 6 & -7 \\\ 2 & 4 & λ \end{bmatrix}\) is not an invertible matrix, then the value of λ = - 8 |
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