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JEE Main 20199 AprilMorning Shift
Exam
JEE Main
Year
2019
Date
9 April
Shift
Morning Shift
Subject
Mathematics
Chapter
Functions

JEE Main 2019 · 9 April · Morning Shift · Mathematics · Functions

If the function f: R - \ 1, - 1\ → A defined by f(x) = x ^ 2 1 - x...

If the function f:R−{1,−1}→Af: R - \left\{1, - 1\right\} \to A defined by f(x)=x21−x2,f\left(x\right) = \dfrac{{x}^{2}}{1 - {x}^{2}}, is surjective, then AA is equal to

Options

  1. A[0,∞)\left[0, \infty\right)
  2. BR−−1R - { - 1 }
  3. CR−[−1,0)R - \left[- 1, 0\right)
  4. DR−(−1,0)R - \left(- 1,0\right)

Correct answer

C. R−[−1,0)R - \left[- 1, 0\right)

Step-by-step solution

A function is surjective, when the range of the function is same as the co-domain.

Now, y=x21−x2y = \dfrac{{x}^{2}}{1 - {x}^{2}}

⇒y−yx2=x2⇒ y - y{x}^{2} = {x}^{2}

⇒y=x2(y+1)⇒ y = {x}^{2}\left(y + 1\right)

⇒x2=yy+1⇒ {x}^{2} = \dfrac{y}{y + 1}

∵x2≥0⇒yy+1≥0∵ {x}^{2} \ge 0 ⇒ \dfrac{y}{y + 1} \ge 0

⇒y∈(−∞,−1)∪[0,∞)⇒ y \in \left(- \infty , - 1\right) \cup \left[0, \infty\right) or R−[−1,0).R - \left[- 1, 0\right) .

∴∴ Range of f=A=R−[−1,0).f = A = R - \left[- 1, 0\right) .

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