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JEE Main 202228 JulyEvening Shift
Exam
JEE Main
Year
2022
Date
28 July
Shift
Evening Shift
Subject
Mathematics
Chapter
Basics of Mathematics

JEE Main 2022 · 28 July · Evening Shift · Mathematics · Basics of Mathematics

Let S = \ x ∈ [- 6, 3] - \ - 2, 2\ : (|x + 3| - 1)/(|x| - 2) ≥ 0\...

Let S={x∈[−6,3]−{−2,2}:∣x+3∣−1∣x∣−2≥0}S = \left\{x \in \left[- 6, 3\right] - \left\{- 2, 2\right\}: \dfrac{\left|x + 3\right| - 1}{\left|x\right| - 2} \ge 0\right\} and T={x∈Z:x2−7∣x∣+9≤0}T = \left\{x \in Z: {x}^{2} - 7\left|x\right| + 9 \le 0\right\}. Then the number of elements in S∩TS \cap T is

Options

  1. A77
  2. B55
  3. C44
  4. D33

Correct answer

D. 33

Step-by-step solution

Given, ∣x∣2−7∣x∣+9≤0{\left|x\right|}^{2} - 7\left|x\right| + 9 \le 0

⇒∣x∣≤7±132⇒ \left|x\right| \le \dfrac{7 \pm \sqrt{13}}{2}

⇒∣x∣∈[7−132,7+132]⇒ \left|x\right| \in \left[\dfrac{7 - \sqrt{13}}{2}, \dfrac{7 + \sqrt{13}}{2}\right]

Also given x∈Integersx \in \text{Integers}, so xx can be ±2,±3,±4,±5\pm 2, \pm 3, \pm 4, \pm 5

Now out of these values of xx only 3,−4,−53, - 4, - 5 will satisfy S=∣x+3∣−1∣x∣−2≥0S = \dfrac{\left|x + 3\right| - 1}{\left|x\right| - 2} \ge 0

So, S∩T∈{3,−4,−5}S \cap T \in \left\{3, - 4, - 5\right\}

So, n(S∩T)=3n\left(S \cap T\right) = 3

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