Q52 / 120 · VITEEE 2013 · Mathematics

If $\left|x^{2}-x-6\right|=x+2$, then the values of $x$ are

  • A
    $-2,2,-4$
  • Correct answer
    B
    $-2,2,4$
  • C
    $3,2,-2$
  • D
    $4,4,3$

Solution

$\left|x^{2}-x-6\right|=x+2$, then Case I : $x^{2}-x-6 < 0$ $\Rightarrow(x-3)(x+2) < 0$ $\Rightarrow-2 < x < 3$ In this case, the equation becomes $x^{2}-x-6=-x-2$ or $x^{2}-4=0$ $\therefore \mathrm{x}=\pm 2$ Clearly, $x=2$ satisfies the domain of the equation in this case. So, $x=2$ is a solution. Case II : $x^{2}-x-6 \geq 0$ So, $x \leq-2$ or $x \geq 3$ In this case, the equation becomes $x^{2}-x-6=0=x+2$ i.e., $x^{2}-2 x-8=0$ or $x=-2,4$ Both these values lie in the domain of the equation in this case, so $x=-2,4$ are the roots. Hence, roots are $x=-2,2,4$.

Hence, the correct answer is option: 'B'.

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