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

मान लीजिए \(r\) वृत्त की त्रिज्या है, जो x-अक्ष को बिंदु \((\mathrm{a}, 0), \mathrm{a} \lt 0\) पर और परवलय \(\mathrm{y}^2=9 \mathrm{x}\) को बिंदु \((4,6)\) पर स्पर्श करता है। तो \(r\) = __________

  1. A 10
  2. B 20
  3. C 30
  4. D 40
Verified Solution

Answer & Solution

Correct Answer

(C) 30

Step-by-step Solution

Detailed explanation

\(\begin{aligned} & (x-a)^2+(y-r)^2=r^2 \\ & (4-a)^2+(6-r)^2=r^2 \\ & 16+a^2-8 a+36+r^2-12 r=r^2 \\ & a^2-8 a-12 r+52=0 \end{aligned}\) Tangent to parabola at \((4,6)\) is \(6.4=9 .\left(\frac{x+4}{2}\right) \text { i.e. } 3 x-4 y+12=0\) This is also tangent to the circle…
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