Number of solutions to max-min modulus equation

CAT 2024 Slot 3 · Quantitative Ability · Medium · Algebra

The number of distinct real values of xx, satisfying the equation max⁡{x,2}−min⁡{x,2}=∣x+2∣−∣x−2∣\max\{x, 2\} - \min\{x, 2\} = |x + 2| - |x - 2| is

Answer

2

Explanation

Note that max⁡{x,2}−min⁡{x,2}=∣x−2∣\max\{x, 2\} - \min\{x, 2\} = |x - 2|.

The equation becomes: ∣x−2∣=∣x+2∣−∣x−2∣  ⟹  2∣x−2∣=∣x+2∣|x - 2| = |x + 2| - |x - 2| \implies 2|x - 2| = |x + 2|

Analyzing case by case:

  1. x≥2x \ge 2: 2(x−2)=x+2  ⟹  x=62(x - 2) = x + 2 \implies x = 6. (Valid, 6≥26 \ge 2)
  2. −2≤x<2-2 \le x < 2: 2(2−x)=x+2  ⟹  4−2x=x+2  ⟹  3x=2  ⟹  x=2/32(2 - x) = x + 2 \implies 4 - 2x = x + 2 \implies 3x = 2 \implies x = 2/3. (Valid, −2≤2/3<2-2 \le 2/3 < 2)
  3. x<−2x < -2: 2(2−x)=−(x+2)  ⟹  4−2x=−x−2  ⟹  x=62(2 - x) = -(x + 2) \implies 4 - 2x = -x - 2 \implies x = 6. (Invalid, since 6≮−26 \nless -2)

Thus, there are 2 distinct real solutions: x=6x = 6 and x=2/3x = 2/3.

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