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Question: Answered & Verified by Expert
If the sum of the slopes of the lines given by $x^2-2 c x y-7 y^2=0$ is four times their product, then $c$ has the value
MathematicsApplication of DerivativesJEE MainJEE Main 2004
Options:
  • A
    1
  • B
    $-1$
  • C
    2
  • D
    $-2$
Solution:
1389 Upvotes Verified Answer
The correct answer is:
2
$m_1+m_2=-\frac{2 c}{7}$ and $m_1 m_2=-\frac{1}{7}$
$m_1+m_2=4 m_1 m_2 \quad$ (given)
$\Rightarrow c=2$

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