Mathematics · Circles

JEE Main 2025 — 23 January, Evening Shift — Question 23

The focus of the parabola y2=4x+16y^{2}=4 x+16 is the centre of the circle C of radius 5 . If the values of λ\lambda, for which C passes through the point of intersection of the lines 3x−y=03 \mathrm{x}-\mathrm{y}=0 and x+λy=4\mathrm{x}+\lambda \mathrm{y}=4, are λ1\lambda_{1} and λ2,λ1<λ2\lambda_{2}, \lambda_{1}<\lambda_{2}, then 12λ1+29λ212 \lambda_{1}+29 \lambda_{2} is equal to _____\_\_\_\_\_ .

Answer: 15

Numerical answer — enter this value.

Step-by-step solution

y2=4(x+4)y^{2}=4(x+4)

Equation of circle

(x+3)2+y2=25(x+3)^{2}+y^{2}=25

Passes through the point of intersection of two lines 3x−y=03 x-y=0

and x+λy=4x+\lambda y=4 (43λ+1,123λ+1)\left(\frac{4}{3 \lambda+1}, \frac{12}{3 \lambda+1}\right), we get

λ=−76,1\lambda=-\frac{7}{6}, 1

12λ1+29λ212 \lambda_{1}+29 \lambda_{2}

−14+29=15-14+29=15

Answer key and solution verified before publishing.

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Exam
JEE Main 2025
Subject
Mathematics
Chapter
Circles
Topic
Considering a Line or a Point wrt a Circle