Home MCQs EEJ MAIN Mathematics Question #7495
Back to Questions
EEJ MAIN Mathematics QUESTION #7495
Question 1
Let \(S = \{x \in \mathbb{R} : x \geq 0 \text{ and } 2|\sqrt{x}-3| + \sqrt{x}(\sqrt{x}-6) + 6 = 0\}\). Then S:
  • contains exactly two elements✔️
  • contains exactly four elements
  • is an empty set
  • contains exactly one element
Correct Answer Explanation
Simplifying: \(2|\sqrt{x}-3| + x - 6\sqrt{x} + 6 = 0\). Let \(t = \sqrt{x}\), so \(2|t-3| + t^2 - 6t + 6 = 0\). For \(t \geq 3\): \(2(t-3) + t^2 - 6t + 6 = 0\), giving \(t^2 - 4t = 0\), so \(t=0\) or \(t=4\). Only \(t=4\) satisfies \(t \geq 3\). For \(t < 3\): \(2(3-t) + t^2 - 6t + 6 = 0\), giving \(t^2 - 8t + 12 = 0\), so \(t=2\) or \(t=6\). Only \(t=2\) satisfies \(t<3\). Thus \(t \in \{2,4\}\), giving \(x \in \{4, 16\}\). S contains 2 elements.