JEE 2023 Mathematics PYQ — Let be a point on the -axis. Common tangents are drawn from to th… | Mathem Solvex | Mathem Solvex
Tip:A–D to answerE for explanationV for videoS to reveal answer
JEE 2023 — Mathematics PYQ
JEE | Mathematics | 2023
Let A be a point on the x-axis. Common tangents are drawn from A to the curves x2+y2=8 and y2=16x. If one of these tangents touches the two curves at Q and R, then (QR)2 is equal to:
Choose the correct answer:
A.
81
B.
72
(Correct Answer)
C.
76
D.
64
Correct Answer:
72
Explanation
Solution
Parabola y2=16x ki tangent ki equation: y=mx+m4.
Circle x2+y2=8 ke liye tangent ki condition: c2=r2(1+m2).
(m4)2=8(1+m2)⟹m216=8(1+m2)
2=m2+m4⟹m4+m2−2=0⟹(m2+2)(m2−1)=0
Chunki m real hai, m2=1⟹m=±1.
Points of contact nikalne par:
Parabola par R=(m2a,m2a)=(4,8) (agar m=1 lein).
Circle par Q=(c−r2m,cr2)=(−2,2).
(QR)2=(4−(−2))2+(8−2)2=62+62=36+36=72
Correct Option: (2)
Explanation
Solution
Parabola y2=16x ki tangent ki equation: y=mx+m4.
Circle x2+y2=8 ke liye tangent ki condition: c2=r2(1+m2).