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JEE Main 2021
Conic Sections
Parabola
Easy

Question

Two common tangents to the circle x2+y2=2a2{x^2} + {y^2} = 2{a^2} and parabola y2=8ax{y^2} = 8ax are :

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Solution

1. Key Concepts and Formulas

To solve this problem, we need to find lines that are simultaneously tangent to a given parabola and a given circle. We will use the following standard formulas and conditions:

  • Equation of a Tangent to a Parabola: For a parabola of the form y2=4Axy^2 = 4Ax, the general equation of a tangent with slope mm is given by y=mx+Amy = mx + \frac{A}{m}.
  • Condition for Tangency to a Circle: A line Lx+My+N=0Lx + My + N = 0 is tangent to a circle with center (h,k)(h,k) and radius RR if the perpendicular distance from the center (h,k)(h,k) to the line is equal to the radius RR. This is expressed

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