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JEE Main 20188 April
Exam
JEE Main
Year
2018
Date
8 April
Subject
Mathematics
Chapter
Basics of Mathematics

JEE Main 2018 · 8 April · Mathematics · Basics of Mathematics

Let S = \ x ∈ R: x ≥ 0 and 2| x - 3| + x ( x - 6) + 6 = 0\ . Then S...

Let S={x∈R:x≥0 and 2∣x−3∣+x(x−6)+6=0}S = \left\{x \in R: x \ge 0 \text{ and } 2\left|\sqrt{x} - 3\right| + \sqrt{x}\left(\sqrt{x} - 6\right) + 6 = 0\right\} . Then SS:Let S = \ x ∈ R: x ≥ 0 and 2| x - 3| + x ( x - 6) + 6 = 0\ . Then S :

Options

  1. AContains exactly four elements
  2. BIs an empty set
  3. CContains exactly one element
  4. DContains exactly two elements

Correct answer

D. Contains exactly two elements

Step-by-step solution

2∣x−3∣+x(x−6)+6=02\left|\sqrt{x} - 3\right| + \sqrt{x}\left(\sqrt{x} - 6\right) + 6 = 0

Let x=t>0\sqrt{x} = t > 0

2∣t−3∣+t(t−6)+6=02\left|t - 3\right| + t\left(t - 6\right) + 6 = 0

⇒2∣t−3∣⇒ 2\left|t - 3\right|=−(t2−6t+6)= - \left({t}^{2} - 6t + 6\right)

⇒2∣t−3∣=−(t2−6t+9)+3⇒ 2\left|t - 3\right| = - \left({t}^{2} - 6t + 9\right) + 3
Let S = \ x ∈ R: x ≥ 0 and 2| x - 3| + x ( x - 6) + 6 = 0\ . Then S :

So the equation 22 solutions.

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