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Question: Answered & Verified by Expert
If the slope of one of the lines given by $a x^2+2 h x y+b y^2=0$ is two times the other, then
MathematicsPair of LinesMHT CETMHT CET 2022 (07 Aug Shift 1)
Options:
  • A $8 h=9 a b^2$
  • B $8 h^2=9 a b^2$
  • C $8 h^2=9 a b$
  • D $8 h=9 a b$
Solution:
2218 Upvotes Verified Answer
The correct answer is: $8 h^2=9 a b$
$\begin{aligned} & \mathrm{m}_1+\mathrm{m}_2=\frac{-2 \mathrm{~h}}{\mathrm{~b}} \text { and } \mathrm{m}_1+\mathrm{m}_2=\frac{\mathrm{a}}{\mathrm{b}} \\ & \Rightarrow \mathrm{m}+2 \mathrm{~m}=\frac{-2 \mathrm{~h}}{\mathrm{~b}} \text { and } \mathrm{m} \times 2 \mathrm{~m}=\frac{\mathrm{a}}{\mathrm{b}} \\ & \Rightarrow 3 \mathrm{~m}=\frac{-2 \mathrm{~h}}{\mathrm{~b}} \text { and } 2 \mathrm{~m}^2=\frac{\mathrm{a}}{\mathrm{b}} \\ & \Rightarrow 2\left(\frac{-2 \mathrm{~h}}{3 \mathrm{~b}}\right)^2=\frac{\mathrm{a}}{\mathrm{b}} \\ & \Rightarrow 8 \mathrm{~h}^2=9 \mathrm{ab}\end{aligned}$

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