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Question: Answered & Verified by Expert
The lines represented by $a x^{2}+2 h x y+b y^{2}=0$ are perpendicular to each other if
MathematicsStraight LinesCOMEDKCOMEDK 2016
Options:
  • A $h=0$
  • B $h^{2}=a b$
  • C $a+b=0$
  • D $h^{2}=a+b$
Solution:
1934 Upvotes Verified Answer
The correct answer is: $a+b=0$
We know that the angle between the two lines
$a x^{2}+2 h x y+b y^{2}=0$ is given by
$\tan \theta=\left|\frac{2 \sqrt{h^{2}-a b}}{a+b}\right|$
$\begin{aligned} \because & \theta &=90^{\circ} \\ & \therefore & a+b &=0 \end{aligned}$

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