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Provide solution for rd sharma math class class 12 chapter Algebra of matrices exercise 4.3 question 26

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Answer: x=2

Hint: Matrix multiplication is only possible, when the number of columns of first matrix is equal to the number of rows of second matrix.

Given: \left[\begin{array}{lll}1 & -1 & x\end{array}\right]\left[\begin{array}{ccc}0 & 1 & -1 \\ 2 & 1 & 3 \\ 1 & 1 & 1\end{array}\right]\left[\begin{array}{l}0 \\ 1 \\ 1\end{array}\right]=0

Firstly, we multiply first two matrices

\Rightarrow\left[\begin{array}{lll}0-2+x & 1-1+x & -1-3+x\end{array}\right]\left[\begin{array}{l}0 \\ 1 \\ 1\end{array}\right]=0 \\\\ \Rightarrow\left[\begin{array}{lll}x-2 & x & x-4\end{array}\right]\left[\begin{array}{l}0 \\ 1 \\ 1\end{array}\right]=0\\\\ \Rightarrow[0(x-2)+x(1)+(x-4)(1)]=0 \\\\ \Rightarrow 0+x+x-4=0\\\\ \Rightarrow 2 x-4=0\\\\ \Rightarrow 2 x=4\\\\ \Rightarrow x=\frac{4}{2}=2

Hence, x=2

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