If $h^2=a b$, then the slopes of lines represented by $a x^2-2 h x y+b y^2=0$ would be in the ratio

If $h^2=a b$, then the slopes of lines represented by $a x^2-2 h x y+b y^2=0$ would be in the ratio
  1. $1: 2$
  2. $2: 1$
  3. $2: 3$
  4. $1: 1$

Solution

Given, $h^2=a b$ and $a x^2+2 h x y+b y^2=0$ Divide by $x^2$, we obtain $ b m^2+2 h m+a=0 $ $[\because y=m x$ is equation of line through origin, i.e. $ \left.\frac{y}{x}=m\right] $ $ \begin{aligned} \Rightarrow \quad m & =\frac{-2 h \pm \sqrt{4 h^2-4 a b}}{2 b} \\ & =\frac{-2 h \pm \sqrt{4\left(h^2-a b\right)}}{2 b \quad\left(\because h^2=a b \text { and } \therefore h^2-a b=0\right)} \\ & =\frac{-2 h}{2 b} \\ \therefore \quad m_1 & =\frac{h}{b} \text { and } m_2=\frac{h}{b} \end{aligned} $ Therefore, slopes of both lines are equal $ \therefore m_1: m_2=1: 1 $

Asked in: AP EAMCET 2021 (23 Aug Shift 1)

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