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For What Value of X, the Following Matrix is Singular? - Mathematics

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Question

For what value of x, the following matrix is singular?

\[\begin{bmatrix}5 - x & x + 1 \\ 2 & 4\end{bmatrix}\]

 

Solution

If a matrix A is singular, then  \[\left| A \right| = 0\]
\[\therefore \begin{vmatrix}5 - x & x + 1 \\ 2 & 4\end{vmatrix} = 0\]
\[\Rightarrow 4(5 - x) - 2(x + 1) 0\] 
\[ \Rightarrow 20 - 4x - 2x - 2\] 
\[ \Rightarrow 18 - 6x = 0\] 
\[ \Rightarrow 18 = 6x\] 
\[ \Rightarrow x = 3\] 

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Chapter 6: Determinants - Exercise 6.6 [Page 90]

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RD Sharma Mathematics [English] Class 12
Chapter 6 Determinants
Exercise 6.6 | Q 2 | Page 90

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