Mathematics · Hyperbola

JEE Main 2025 — 3 April, Morning Shift — Question 41

Let the product of the focal distances of the point P(4,23)\mathrm{P}(4,2 \sqrt{3}) on the hyperbola H:x2a2−y2 b2=1\mathrm{H}: \frac{\mathrm{x}^{2}}{\mathrm{a}^{2}}-\frac{\mathrm{y}^{2}}{\mathrm{~b}^{2}}=1 be 32.

Let the length of the conjugate axis of H be p and the length of its latus rectum be q . Then p2+q2\mathrm{p}^{2}+\mathrm{q}^{2} is equal to ......

Answer: 120

Numerical answer — enter this value.

Step-by-step solution

x2a2−y2b2=1…(1)\frac{x^{2}}{a^{2}}-\frac{y^{2}}{b^{2}}=1 …(1)

P(4,23)\mathrm{P}(4,2 \sqrt{3})

PS1.PS2=32\mathrm{PS}_{1} . \mathrm{PS}_{2}=32

∣PS1−PS2∣=2a\left|\mathrm{PS}_{1}-\mathrm{PS}_{2}\right|=2 \mathrm{a}

P(4,23)\mathrm{P}(4,2 \sqrt{3}) lies on H

∴16a2−12 b2=1\therefore \frac{16}{\mathrm{a}^{2}}-\frac{12}{\mathrm{~b}^{2}}=1

16b2−12a2=a2b2…(2)16 b^{2}-12 a^{2}=a^{2} b^{2} …(2)

∣PS1−PS2∣2=4a2\left|\mathrm{PS}_{1}-\mathrm{PS}_{2}\right|^{2}=4 \mathrm{a}^{2}

PS12+PS22−2PS1.PS2=4a2\mathrm{PS}_{1}{ }^{2}+\mathrm{PS}_{2}{ }^{2}-2 \mathrm{PS}_{1} . \mathrm{PS}_{2}=4 \mathrm{a}^{2}

(ae−4)2+12+(ae+4)2+12−64=4a2(\mathrm{ae}-4)^{2}+12+(\mathrm{ae}+4)^{2}+12-64=4 \mathrm{a}^{2}

2a2e2−8=4a22 \mathrm{a}^{2} \mathrm{e}^{2}-8=4 \mathrm{a}^{2}

a2+b2−4=2a2a^{2}+b^{2}-4=2 a^{2}

b2−a2=4\mathrm{b}^{2}-\mathrm{a}^{2}=4

(2) & (3) ⇒16(a2+4)−12a2=a2(a2+4)\Rightarrow 16\left(\mathrm{a}^{2}+4\right)-12 \mathrm{a}^{2}=\mathrm{a}^{2}\left(\mathrm{a}^{2}+4\right)

⇒16a2+64−12a2=a4+4a2\Rightarrow 16 \mathrm{a}^{2}+64-12 \mathrm{a}^{2}=\mathrm{a}^{4}+4 \mathrm{a}^{2} ⇒a4=64\Rightarrow \mathrm{a}^{4}=64

⇒a2=8\Rightarrow \mathrm{a}^{2}=8

∴b2=12\therefore \mathrm{b}^{2}=12

p2+q2=4b2+4b4a2p^{2}+q^{2}=4 b^{2}+\frac{4 b^{4}}{a^{2}}

=120=120

Answer key and solution verified before publishing.

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Exam
JEE Main 2025
Subject
Mathematics
Chapter
Hyperbola
Topic
Introduction to Hyperbola
Let the product of the focal distances of the point P (4,2 √(3)) on… | JEE Main 2025 PYQ with Solution · DhiX AI