Find values of x for which left|begin{array}{ll}3 & x x & 1end{array}right|=left|begin{array

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3 and 4 .Determinants and Matrices

easy

Find values of $x$ for which $\left|\begin{array}{ll}3 & x \\ x & 1\end{array}\right|=\left|\begin{array}{ll}3 & 2 \\ 4 & 1\end{array}\right|$

A

$x=\pm 2 \sqrt{2}$

B

$x=\pm 3 \sqrt{2}$

C

$x=\pm \sqrt{2}$

D

$x=\pm 4 \sqrt{2}$

Solution

Solution We have $\left|\begin{array}{ll}3 & x \\ x & 1\end{array}\right|=\left|\begin{array}{ll}3 & 2 \\ 4 & 1\end{array}\right|$

i.e. $\quad 3-x^{2}=3-8$

i.e. $x^{2}=8$

Hence $x=\pm 2 \sqrt{2}$

Standard 12

Mathematics

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