The range of the function f(x) = x2/(1 + x2) is:

2018

The range of the function f(x) = x2/(1 + x2) is:

  1. A.

    (- ∞, + ∞ )

  2. B.

    (0, ∞)

  3. C.

    (-∞, 0)

  4. D.

    (0, 1)

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Correct answer: D

  1. Analyze the expression:

    $$f(x) = \frac{x^2}{1 + x^2}$$

  2. Determine the Minimum Value:

    Because x2 is a squared term, its value can never be negative for any real number x. The smallest possible value x2 can achieve is 0 (when x = 0).

    $$f(0) = \frac{0^2}{1 + 0^2} = 0$$

    Therefore, the minimum value of the function is 0, and it is inclusive (the function actually reaches 0).

  3. Determine the Maximum Value:

    For any real number x, the numerator (x2) will always be exactly 1 less than the denominator (1 + x2).

    Since the numerator is strictly smaller than the denominator, the value of the fraction must always be less than 1.

    As x grows towards infinity, the +1 in the denominator becomes negligible, and the fraction approaches $1$ but never quite touches it. This means 1 is an exclusive upper bound.

Combining these insights, the exact mathematical range is [0, 1).

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