If $y=\tan ^{-1}\left(\frac{5 x+1}{3-x-6 x^2}\right)$, then $\frac{d y}{d x}=$

If $y=\tan ^{-1}\left(\frac{5 x+1}{3-x-6 x^2}\right)$, then $\frac{d y}{d x}=$
  1. $\frac{3}{9 x^2+12 x+5}+\frac{1}{2 x^2-2 x+1}$
  2. $\frac{1}{9 x^2+12 x+5}+\frac{1}{4 x^2-4 x+2}$
  3. $\frac{1}{9 x^2+12 x+5}-\frac{1}{4 x^2-4 x+2}$
  4. $\frac{3}{9 x^2+12 x+5}-\frac{1}{2 x^2-2 x+1}$

Solution

$\begin{aligned} & y=\tan ^{-1}\left(\frac{5 x+1}{3-x-6 x^2}\right)=\tan ^{-1} \frac{(3 x+2)+(2 x-1)}{1-(3 x+2)(2 x-1)} \\ & \Rightarrow y=\tan ^{-1}(3 x+2)+\tan ^{-1}(2 x-1) \\ & \Rightarrow \frac{\mathrm{d} y}{\mathrm{~d} x}=\frac{1}{1+(3 x+2)} \times 3+\frac{1}{1+(2 x-1)^2} \times 2 \\ & \Rightarrow \frac{\mathrm{d} y}{\mathrm{~d} x}=\frac{3}{9 x^2+12 x+5}+\frac{2}{4 x^2-4 x+2} \\ & \Rightarrow \frac{\mathrm{d} y}{\mathrm{~d} x}=\frac{3}{9 x^2+12 x+5}+\frac{1}{2 x^2-2 x+1}\end{aligned}$

Asked in: MHT CET 2022 (08 Aug Shift 2)

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