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JEE Main 202324 JanuaryMorning Shift
Exam
JEE Main
Year
2023
Date
24 January
Shift
Morning Shift
Subject
Mathematics
Chapter
Functions

JEE Main 2023 · 24 January · Morning Shift · Mathematics · Functions

The equation x ^ 2 – 4x + [ x ] + 3 = x [ x ] , where [ x ] denotes...

The equation x2–4x+[x]+3=x[x]{x}^{2} – 4x + [ x ] + 3 = x [ x ], where [x][ x ] denotes the greatest integer function, has:

Options

  1. Aexactly two solutions in (−∞,∞)( - \infty , \infty )
  2. Bno solution
  3. Ca unique solution in (−∞,1)( - \infty , 1 )
  4. Da unique solution in (−∞,∞)( - \infty , \infty )

Correct answer

D. a unique solution in (−∞,∞)( - \infty , \infty )

Step-by-step solution

Given:

x2−4x+[x]+3=x{x}^{2} - 4x + \left[x\right] + 3 = x\left[x\right]

⇒x2−4x+3=x[x]⇒ {x}^{2} - 4x + 3 = x\left[x\right] - \left[x\right]</p><p></p><p>⇒ \left(x - 1\right)\left(x - 3\right) = \left[x\right]\left(x - 1\right)</p><p>⇒x=1or</p><p>⇒ x = 1 orx - 3 = \left[x\right]

If x−3=[x]x - 3 = \left[x\right]

⇒x–[x]=3⇒ x – \left[x\right] = 3

⇒{x}=3⇒ \left\{x\right\} = 3

which is not Possible, since \left\{x\right\} \in [ 0, 1 ).</p><p>Hence,.</p><p>Hence,x = 1istheonlyonesolutionin(−∞,∞)is the only one solution in \left(- \infty , \infty\right).

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