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If [ X ] 2 − 5 [ X ] + 6 = 0 , Where [.] Denotes the Greatest Integer Function, Then (A) X ∈ [3, 4] (B) X ∈ (2, 3] (C) X ∈ [2, 3] (D) X ∈ [2, 4) - Mathematics

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Question

If  \[\left[ x \right]^2 - 5\left[ x \right] + 6 = 0\], where [.] denotes the greatest integer function, then 

 

Options

  • (a) ∈ [3, 4]   

  •    (b) ∈ (2, 3]           

  •   (c) ∈ [2, 3]      

  •   (d) ∈ [2, 4)

MCQ

Solution

The given equation is \[\left[ x \right]^2 - 5\left[ x \right] + 6 = 0\]

\[\left[ x \right]^2 - 5\left[ x \right] + 6 = 0\]
\[ \Rightarrow \left[ x \right]^2 - 3\left[ x \right] - 2\left[ x \right] + 6 = 0\]
\[ \Rightarrow \left[ x \right]\left( \left[ x \right] - 3 \right) - 2\left( \left[ x \right] - 3 \right) = 0\]
\[ \Rightarrow \left( \left[ x \right] - 2 \right)\left( \left[ x \right] - 3 \right) = 0\]

\[\Rightarrow \left[ x \right] - 2 = 0 \text{ or } \left[ x \right] - 3 = 0\]
\[ \Rightarrow \left[ x \right] = 2\text{  or }  \left[ x \right] = 3\]

⇒ x ∈ [2, 3) or x ∈ [3, 4)
⇒ x ∈ [2, 4)

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Chapter 3: Functions - Exercise 3.6 [Page 45]

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RD Sharma Mathematics [English] Class 11
Chapter 3 Functions
Exercise 3.6 | Q 44 | Page 45

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