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ExamsJEE MainMaths

Let g(x) = 1 + x - [x] and f(x) = -1 for x < 0, 0 for x = 0, 1 for x > 0, where [.] is the greatest integer function. For all real x, f(g(x)) equals:

  1. x
  2. 1
  3. f(x)
  4. g(x)

Correct answer: 1

Solution

x - [x] = {x} is the fractional part, with 0 <= {x} < 1. Thus g(x) = 1 + {x} satisfies 1 <= g(x) < 2, which is always positive. Since f returns 1 for any positive argument, f(g(x)) = 1 for all x.

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