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JEE Mains · Maths · STD 11 - 10.2 parabola,ellipse,hyperbola

If a line along a chord of the circle \(4 x^{2}+4 y^{2}+120 x+675=0\), passes through the point \((-30,0)\) and is tangent to the parabola \(\mathrm{y}^{2}=30 \mathrm{x}\), then the length of this chord is :

  1. A \(5\)
  2. B \(7\)
  3. C \(5 \sqrt{3}\)
  4. D \(3 \sqrt{5}\)
Verified Solution

Answer & Solution

Correct Answer

(D) \(3 \sqrt{5}\)

Step-by-step Solution

Detailed explanation

Equation of tangent to \(\mathrm{y}^{2}=30 \mathrm{x}\) \(y=m x+\frac{30}{4 m}\) Pass thru \((-30,0): \mathrm{a}=-30 \mathrm{~m}+\frac{30}{4 \mathrm{~m}} \Rightarrow \mathrm{m}^{2}=1 / 4\) \(\Rightarrow \mathrm{m}=\frac{1}{2}\) or \(\mathrm{m}=-\frac{1}{2}\) At…
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