Product of Distinct Roots of Absolute Quadratic

CAT 2019 Slot 1 · QA · Medium · Quadratic equations

The product of the distinct roots of x2x6=x+2|x^2 - x - 6| = x + 2 is

  1. A.

    -4

  2. B.

    -16

  3. C.

    -8

  4. D.

    -24

Answer

B

Explanation

Note x2x6=(x3)(x+2)=x+2|x^2 - x - 6| = |(x-3)(x+2)| = x + 2. Case 1: x+2<0    x<2x + 2 < 0 \implies x < -2: No real solution since LHS 0\ge 0. Case 2: x=2x = -2: LHS =0== 0 = RHS, so x=2x = -2 is a solution. Case 3: x>2x > -2: x+2>0x+2 > 0, so we divide both sides by x+2x+2. x3=1    x3=1|x - 3| = 1 \implies x - 3 = 1 or x3=1    x=4x - 3 = -1 \implies x = 4 or x=2x = 2. Both 44 and 22 are >2> -2. Distinct roots are 2,2,4-2, 2, 4. Product =(2)×2×4=16= (-2) \times 2 \times 4 = -16.

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