MCQ
If $\text{A}=\begin{vmatrix} 1 &\text{amp; 2} \\ 2 &\text{amp; 1} \end{vmatrix}$ and $\text{f}\text{(x)}=\frac{1+\text{x}}{1-\text{x}},$ then $\text{f}(|\text{A}|)$ is:
  • $\dfrac{-1}{2}$
  • B
    $\dfrac{1}{2}$
  • C
    $\dfrac{-1}{3}$
  • D
    $\text{None of these}$

Answer

Correct option: A.
$\dfrac{-1}{2}$
Here, $|\text{A}| =1\times 1-2\times 2 = -3$

$\therefore\text{f}(|\text{A}|)=\cfrac{1+(-3)}{1+3}=-\cfrac{1}{2}$

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