JEE Main · Mathematics ↓ Falling

Conic Sections appeared 76 times across 3 years — 8.8% of Mathematics. This question is from Properties of Focal Chords.

Year 2026 2025 2024 Total
Questions 22 38 16 76

Let y² = 12x the parabola and S be its focus. Let PQ be a focal chord of the parabola such that (SP) (SQ) = (147)/(4). Let C be the circle described taking PQ as a diameter. If the equation of a circle C is 64x² + 64y² - α x - 64√(3)y = β, then \beta - \alpha is equal to

Numerical Answer Type:
Enter a numerical value Answer: 1328 to 1328 +4 marks

Solution & Explanation

Related Formula

Properties of focal chord parameter metrics in parabolas y² = 4ax:

t₁ · t₂ = -1

Distance to the directrix property:

SP = a(1 + t²), SQ = a(1 + (1)/(t²))
Core Logic

Given parabola y² = 12x a = 3. Focus S = (3, 0). Set up focal segments product equation:

SP · SQ = 3(1+t²) · 3(1+(1)/(t²)) = (147)/(4) 9 · ((1+t²)²)/(t²) = (147)/(4) ((1+t²)²)/(t²) = (49)/(12)

Solving for t²:

12t⁴ - 25t² + 12 = 0 t² = (3)/(4) or (4)/(3)
Step 1: Compute Endpoint Coordinate Bounds

Choosing t = - √(3)2 allows defining both chord coordinates symmetrically:

P(3t², 6t) P((9)/(4), -3√(3)) Q((3)/(t²), -(6)/(t)) Q(4, 4√(3))
Step 2: Derive Circle Equation

Write the diameter circle form equation:

(x - 4)(x - (9)/(4)) + (y - 4√(3))(y + 3√(3)) = 0 x² + y² - (25)/(4)x - √(3)y - 27 = 0

Multiply by 64 to clear the fractions and match the given equation template structure:

64x² + 64y² - 400x - 64√(3)y - 1728 = 0

Comparing directly with 64x² + 64y² - α x - 64√(3)y = β yields:

α = 400, β = 1728 β - α = 1728 - 400 = 1328
Pattern Recognition

The distance from focal chord endpoints to the focus equals their perpendicular distance to the directrix. This property connects parameter metrics to geometric lengths cleanly.

Chapter Mix

Class 11 Mathematics: Conic Sections Class 11 Mathematics: Circles

Reference Study Guides

More Conic Sections Previous-Year Questions — Page 3

Q1 jee_main_2026_23_january_morning Hyperbola
Let the domain of the function f(x) = ₃ ₅ ₇(9x - x² - 13) be the interval (m, n). Let the hyperbola (x²)/(a²) - (y²)/(b²) = 1 have eccentricity (n)/(3) and the length of the latus rectum (8m)/(3). Then b² - a² is equal to:
  • A. 5
  • B. 11
  • C. 9
  • D. 7

Solution

Related Formula
e = √(1 + (b²)/(a²)) L.R. = (2b²)/(a)
Core Logic

For the domain of the given logarithmic function, the argument of the innermost logarithm must be strictly greater than 1 because of the nested logs:

₅( ₇(9x-x²-13))>0 ⇒ ₇(9x-x²-13) > 1 ⇒ 9x-x²-13 > 7 ⇒ x²-9x+20 < 0 ⇒ (x-4)(x-5) < 0

Thus, 4 < x < 5. Therefore, the domain interval is (4, 5), yielding m = 4 and n = 5.

Step 1: Hyperbola Properties

Given eccentricity e = (n)/(3) = (5)/(3):

e = √(1 + (b²)/(a²)) = (5)/(3) ⇒ (b²)/(a²) = (25)/(9) - 1 = (16)/(9) ⇒ (b)/(a) = (4)/(3)

Given the length of the latus rectum is (8m)/(3):

(2b²)/(a) = (8(4))/(3) = (32)/(3) ⇒ 2b((b)/(a)) = (32)/(3) ⇒ 2b((4)/(3)) = (32)/(3) ⇒ 8b = 32 ⇒ b = 4

Since (b)/(a) = (4)/(3), we get a = 3.

Step 2: Final Calculation

We need to find b² - a²:

b² - a² = (4)² - (3)² = 16 - 9 = 7
Pattern Recognition

Nested logarithmic domains require unpacking from the outside in: ₐ(X) > 0 ⇒ X > 1. Linking function domains to coordinate geometry parameters is a standard JEE cross-topic pattern.

Chapter Mix

Class 11 Maths: Conic Sections Class 11 Maths: Relations and Functions

Q5 jee_main_2026_23_january_morning Ellipse
Let the line y - x = 1 intersect the ellipse (x²)/(2) + (y²)/(1) = 1 at the points A and B. Then the angle made by the line segment AB at the center of the ellipse is:
  • A. π - ⁻¹((1)/(4))
  • B. (π)/(2) + ⁻¹((1)/(4))
  • C. (π)/(2) + 2 ⁻¹((1)/(4))
  • D. (π)/(2) - ⁻¹((1)/(4))

Solution

Related Formula
θ = | (m₁ - m₂)/(1 + m₁ m₂) |
Core Logic

Find the intersection points of the line y = x + 1 and the ellipse (x²)/(2) + y² = 1.

Ellipse diagram for Q5 - JEE Main 2026 Morning
Ellipse diagram for Q5 - JEE Main 2026 Morning
Substitute y = x + 1 into the ellipse equation:

(x²)/(2) + (x + 1)² = 1 x² + 2(x² + 2x + 1) = 2 3x² + 4x = 0 ⇒ x(3x + 4) = 0

This gives x = 0 or x = -(4)/(3).

Step 1: Calculate Intersection Points

For x = 0, y = 1 ⇒ A(0, 1). For x = -(4)/(3), y = -(4)/(3) + 1 = -(1)/(3) ⇒ B(-(4)/(3), -(1)/(3)).

Ellipse diagram for Q5 - JEE Main 2026 Morning
Ellipse diagram for Q5 - JEE Main 2026 Morning

Step 2: Find Angle at the Origin

Let O(0,0) be the center of the ellipse. The angle made by segment AB at O is ∠ AOB. The slope of OA is m₁ = (1 - 0)/(0 - 0) = ∞ (which means OA is along the y-axis, angle is π/2). The slope of OB is m₂ = (-1/3 - 0)/(-4/3 - 0) = (1)/(4). The angle of OB with the positive x-axis is θ = ⁻¹((1)/(4)). The total angle ∠ AOB is (π)/(2) + θ = (π)/(2) + ⁻¹((1)/(4)).

Pattern Recognition

When solving line-conic intersection, explicit extraction of points (A, B) is often simpler than using homogenization if the intersection yields simple rational or integer coordinates.

Chapter Mix

Class 11 Maths: Conic Sections Class 11 Maths: Straight Lines

Q19 jee_main_2026_23_january_evening Properties of Parabola
An equilateral triangle OAB is inscribed in the parabola y²=4x with the vertex O at the vertex of the parabola. Then the minimum distance of the circle having AB as a diameter from the origin is
  • A. 4(3 - √(3))
  • B. 2(8 - 3√(3))
  • C. 4(6 + √(3))
  • D. 2(3 + √(3))

Solution

Related Formula

Parametric form of y² = 4ax is (at², 2at). Minimum distance from origin to a circle with centre C and radius r is |OC - r|.

Core Logic

Properties of Parabola diagram for Q19 - JEE Main 2026 Evening
Properties of Parabola diagram for Q19 - JEE Main 2026 Evening
For parabola y² = 4x, a = 1. Let the vertices of the equilateral triangle be O(0,0), A(t², 2t), B(t², -2t) due to symmetry across the x-axis. The slope of OA makes an angle of 30^° with the x-axis.

mOA = (2t - 0)/(t² - 0) = (2)/(t) 30^° = (2)/(t) 1√(3) = (2)/(t) t = 2√(3)
Step 1: Defining the Circle

Vertices are A((2√(3))², 2(2√(3))) = A(12, 4√(3)) and B(12, -4√(3)). The circle has diameter AB. Therefore, its centre is the midpoint of AB, which is C(12, 0). The radius R is half the length of AB, so R = 4√(3).

The equation of the circle is:

(x - 12)² + y² = (4√(3))²
Step 2: Calculating Distance

The distance from the origin O(0,0) to the centre C(12, 0) is d = 12. The minimum distance from the origin to the circle is |d - R|:

= 12 - 4√(3) = 4(3 - √(3))
Pattern Recognition

Any polygon inscribed in a standard parabola symmetric across the axis can be defined completely by equating the slope of a vertex from the origin to the respective tangent of the split angle.

Chapter Mix

Class 11 Maths: Parabola Class 11 Maths: Circles

Q2 jee_main_2026_24_january_morning Circles and Centroid Locus
Let a circle of radius 4 pass through the origin O, the points A(-√(3)a, 0) and B(0, -√(2)b), where a and b are real parameters and ab ≠ 0. Then the locus of the centroid of Δ OAB is a circle of radius
Circles and Centroid Locus diagram for Q2 - JEE Main 2026 Morning
Graphical representation of the triangle OAB mapped on the Cartesian plane.
  • A. (5)/(3)
  • B. (7)/(3)
  • C. (8)/(3)
  • D. (11)/(3)

Solution

Related Formula
Centroid (h,k) = ( (x₁ + x₂ + x₃)/(3), (y₁ + y₂ + y₃)/(3) )
Core Logic

Coordinate geometry setup for Centroid Locus Q2
Graphical representation of the triangle OAB mapped on the Cartesian plane.
Since ∠ AOB = 90^°, AB is the diameter of the circle passing through O, A, B. Therefore, the diameter AB = 2r = 8.

Step 1: Distance and Coordinate Mapping

AB² = 64

(-√(3)a - 0)² + (0 - (-√(2)b))² = 64 3a² + 2b² = 64
Step 2: Locus of Centroid

Let the centroid be G(h,k).

h = -√(3)a + 0 + 03 ⇒ a = -√(3)h k = 0 - √(2)b + 03 ⇒ b = - 3√(2)k

Substituting a and b into the equation:

3(-√(3)h)² + 2(- 3√(2)k)² = 64 9h² + 9k² = 64 x² + y² = (64)/(9)
Step 3: Radius of Locus

This is a circle with r² = (64)/(9), so r = (8)/(3).

Pattern Recognition

Whenever a circle passes through the origin and points on the axes, the segment joining the axes points is always the diameter. Centroid coordinates easily scale the locus.

Chapter Mix

Class 11 Maths: Conic Sections Class 11 Maths: Straight Lines

Q7 jee_main_2026_24_january_morning Ellipse Properties
Let each of the two ellipses E₁: x²a²+ y²b²=1,(a>b) and E₂: x²A²+ y²B²=1,(A
  • A. (96)/(5)
  • B. (32)/(5)
  • C. (16)/(5)
  • D. (8)/(5)

Solution

Related Formula
Eccentricity e = 1 - minor²major² Distance between foci = 2a e (or 2Be if vertical) Latus rectum length = 2minor²major
Core Logic

For E₁: a>b ⇒ e = (4)/(5). Distance between foci 2ae = 8 ⇒ a(4/5) = 4 ⇒ a = 5.

b² = a²(1 - e²) = 25(1 - 16/25) = 9

₁ = (2b²)/(a) = (18)/(5)

Step 1: Analysing E2

For E₂: A

A² = B²(1 - e²) = B²(1 - (16)/(25)) = (9)/(25)B² ⇒ A = (3)/(5)B

₂ = (2A²)/(B) = (2(9/25)B²)/(B) = (18)/(25)B

Step 2: Linking Condition

Given 2 ₁² = 9 ₂:

2((18)/(5))² = 9((18)/(25)B) 2 × (324)/(25) = (162)/(25)B (648)/(25) = (162B)/(25) ⇒ B = 4
Step 3: Finding Final Distance

Distance between foci of E₂ is 2Be.

= 2(4)((4)/(5)) = (32)/(5)
Pattern Recognition

Notice the axis orientation shift: E₁ is horizontal, E₂ is vertical. Apply latus rectum formula (2A²)/(B) appropriately to avoid formula blind-spots.

Chapter Mix

Class 11 Maths: Conic Sections

More Conic Sections Questions — jee_main_2025_29_jan_evening

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