The number of solutions of the equation t a n - 1 x 1 - x 2 + t a n - 1 1 x 3 = 3 π 4 belonging to the…

The number of solutions of the equation tan-1x1-x2+tan-11x3=3π4 belonging to the interval 0,  1 is
  1. 0
  2. 1
  3. 2
  4. 3

Solution

$ x \in (0, 1) \Rightarrow \frac{x}{1-x^2} > 0 ; \frac{1}{x^3} > 0 \Rightarrow \frac{x}{1-x^2} \cdot \frac{1}{x^3} > 1 $ $ \tan^{-1}\left(\frac{x}{1-x^2}\right) + \tan^{-1}\left(\frac{1}{x^3}\right) = \pi + \tan^{-1}\left|\frac{\frac{x}{1-x^2} + \frac{1}{x^3}}{1 - \frac{x}{1-x^2} \cdot \frac{1}{x^3}}\right| = \pi + \tan^{-1}\left|\frac{-1}{x}\right| = \frac{3\pi}{4} $ $ \Rightarrow x = 1 $ (not possible)

Asked in: MHT CET Full Test 10

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