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Mathematics

If A = [2x01]and B =[43601],\begin{bmatrix}[r] 2 & x \ 0 & 1 \end{bmatrix} \text{and B } = \begin{bmatrix}[r] 4 & 36 \ 0 & 1 \end{bmatrix}, find the value of x, given that A2 = B.

Matrices

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Answer

Given,

A2 = B

[2x01][2x01]=[43601][2×2+x×02×x+x×10×2+1×00×x+1×1]=[43601][4+02x+x0+00+1]=[43601][43x01]=[43601]\Rightarrow \begin{bmatrix}[r] 2 & x \ 0 & 1 \end{bmatrix} \begin{bmatrix}[r] 2 & x \ 0 & 1 \end{bmatrix} = \begin{bmatrix}[r] 4 & 36 \ 0 & 1 \end{bmatrix} \\[1em] \Rightarrow \begin{bmatrix}[r] 2 \times 2 + x \times 0 & 2 \times x + x \times 1 \ 0 \times 2 + 1 \times 0 & 0 \times x + 1 \times 1 \end{bmatrix} = \begin{bmatrix}[r] 4 & 36 \ 0 & 1 \end{bmatrix} \\[1em] \Rightarrow \begin{bmatrix}[r] 4 + 0 & 2x + x \ 0 + 0 & 0 + 1 \end{bmatrix} = \begin{bmatrix}[r] 4 & 36 \ 0 & 1 \end{bmatrix} \\[1em] \Rightarrow \begin{bmatrix}[r] 4 & 3x \ 0 & 1 \end{bmatrix} = \begin{bmatrix}[r] 4 & 36 \ 0 & 1 \end{bmatrix} \\[1em]

By definition of equality of matrices we get,

⇒ 3x = 36
∴ x = 12.

Hence, the value of x = 12.

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