Mathematics › Applications of Derivatives › Tangent Normal
If the tangent to the curve $y=\frac{x}{x^2-3}, x \in R,(x \neq \pm \sqrt{3})$ at a point $(\alpha, \beta)…
If the tangent to the curve $y=\frac{x}{x^2-3}, x \in R,(x \neq \pm \sqrt{3})$ at a point $(\alpha, \beta) \neq(0,0)$ on it, is parallel to the line $2 x+6 y-11=0$, then
$|2 \alpha+6 \beta|=11$ $|6 \alpha+2 \beta|=9$ $|6 \alpha+2 \beta|=19$ $|2 \alpha+6 \beta|=19$
Solution
$y=\frac{x}{x^2-3} \Rightarrow \frac{d y}{d x}=\frac{-\left(3+x^2\right)}{\left(x^2-3\right)^2}$
Now slope of $2 x+6 y-11=0$ is $\frac{-1}{3}$
$\begin{aligned} & \frac{\mathrm{A}}{\mathrm{Q}}-\frac{1}{3}=\frac{-\left(3+x^2\right)}{\left(x^2-3\right)^2} \\ & \Rightarrow x^4-9 x^2=0 \\ & \Rightarrow x^2\left(x^2-9\right)=0 \\ & \Rightarrow x=0 \text { or } x= \pm 3\end{aligned}$
But $x \neq 0$ so $x= \pm 3 \Rightarrow y= \pm \frac{1}{2}$
Hence, $\alpha= \pm 3, \beta= \pm \frac{1}{2}$
$\Rightarrow|6 \alpha+2 \beta|=\left| \pm\left(6 \times 3+2 \times \frac{1}{2}\right)\right|=19$
Asked in: MHT CET 2022 (06 Aug Shift 1)
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