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JEE Main20198 Apr 2019Evening ShiftMathematicsContinuity and DifferentiabilityActual

Let f : - 1,3 → R be defined as f x = x + x , x + x , x + x , - 1 ≤ x < 1 1 ≤ x < 2 2 ≤ x ≤ 3 , Where t denotes the greatest integer less than or equal to t . Then, f is discontinuous at:

Options

  1. AOnly one point
  2. BOnly two points
  3. CFour or more points
  4. DOnly three points

Correct answer

D. Only three points

Step-by-step solution

f x = x + x ; - 1 ≤ x < 1 x + x ; 1 ≤ x < 2 x + x ; 2 ≤ x ≤ 3 = - x - 1 ; - 1 ≤ x < 0 x + 0 ; 0 ≤ x < 1 2 x ; 1 ≤ x < 2 x + 2 ; 2 ≤ x < 3 6 ; x = 3                       At x = 0 ,   1 ,   2 ,   3 f changes its definition. ∴ At x = 0   LHL = - 1 ,   RHL = 0 ⇒ f is discontinuous at x = 0 x = 1   LHL = 1 ,   RHL = 2 ⇒ f is discontinuous at

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