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Conic Sections appeared 94 times across 3 years — 10.9% of Mathematics. This question is from Ellipse and Line Properties.

Year 2026 2025 2024 Total
Questions 29 44 21 94

A line passing through the point P(√(5), √(5)) intersects the ellipse (x²)/(36) + (y²)/(25) = 1 at A and B [cite: 567] such that (PA) · (PB) is maximum. Then 5(PA² + PB²) is equal to

Solution & Explanation

Related Formula

Parametric line equation relative to an offset point P(x₀, y₀):

x = x₀ + r θ, y = y₀ + r θ

Ellipse and Line Properties diagram for Q56 - JEE Main 2025 Morning
Ellipse and Line Properties diagram for Q56 - JEE Main 2025 Morning

Core Logic

Assume any line through P(√(5), √(5)) can be represented parametrically by:

Q(√(5) + r θ, √(5) + r θ)

Substitute coordinates into the standard ellipse equation 25x² + 36y² = 900:

25(√(5) + r θ)² + 36(√(5) + r θ)² = 900

Expanding and gathering powers of r yields:

r²(25 ²θ + 36 ²θ) + 2√(5)r(25 θ + 36 θ) - 595 = 0

The product of roots corresponds to the distance product:

PA · PB = |r₁ r₂| = (595)/(25 ²θ + 36 ²θ) = (595)/(25 + 11 ²θ)
Step 1: Maximization Condition

To maximize PA · PB, the denominator must be minimized:

²θ = 0 θ = 0

This implies the chord line AB must run parallel to the x-axis:

yA = yB = √(5)

Substitute y = √(5) back into the ellipse equation to calculate x-coordinates:

(x²)/(36) + (5)/(25) = 1 (x²)/(36) = (4)/(5) x² = (144)/(5)

Therefore, the coordinates are x = ± 12√(5).

Step 2: Distance Value Summation

Compute PA² + PB² using coordinates directly:

PA² + PB² = (√(5) - 12√(5))² + (√(5) + 12√(5))² = 2(5 + (144)/(5)) = (338)/(5)

Multiplying by 5 gives the required value:

5(PA² + PB²) = 338
Pattern Recognition

Shortcut: Represent lines through an arbitrary point parametrically in conic intersection problems. The product of distances |r₁ r₂| directly falls out of the constant term over the leading coefficient, making trigonometric optimization straightforward.

Evaluation Rubric / Model Answer

338

Chapter Mix

Class 11 Mathematics: Conic Sections (Ellipse)

More Conic Sections Previous-Year Questions — Page 6

Q3 jee_main_2026_28_january_evening Parabola and Triangles
Let A be the focus of the parabola y² = 8x. Let the line y = mx + c intersect the parabola at two distinct points B and C. If the centroid of the triangle ABC is ((7)/(3), (4)/(3)), then (BC)² is equal to :
  • A. 41
  • B. 80
  • C. 89
  • D. 32

Solution

Related Formula
Centroid = ((x₁+x₂+x₃)/(3), (y₁+y₂+y₃)/(3)) D² = (x₂-x₁)² + (y₂-y₁)²
Core Logic

Focus of y² = 8x is A(2, 0) since 4a = 8 ⇒ a=2. Let points on parabola be B(2t₁², 4t₁) and C(2t₂², 4t₂). The centroid of Δ ABC is given as ((7)/(3), (4)/(3)). Equating coordinates:

(2 + 2t₁² + 2t₂²)/(3) = (7)/(3) ⇒ t₁² + t₂² = (5)/(2) (0 + 4t₁ + 4t₂)/(3) = (4)/(3) ⇒ t₁ + t₂ = 1

Parabola points and centroid configuration
Parabola points and centroid configuration

Execution

Square the sum equation:

(t₁ + t₂)² = t₁² + t₂² + 2t₁t₂ 1 = (5)/(2) + 2t₁t₂ ⇒ 2t₁t₂ = -(3)/(2) ⇒ t₁t₂ = -(3)/(4)

Find (t₁ - t₂)²:

(t₁ - t₂)² = (t₁ + t₂)² - 4t₁t₂ = 1 - 4(-(3)/(4)) = 4

Calculate distance squared for BC:

(BC)² = (2t₁² - 2t₂²)² + (4t₁ - 4t₂)² (BC)² = 4(t₁ - t₂)²(t₁ + t₂)² + 16(t₁ - t₂)² (BC)² = 4(4)(1) + 16(4) = 16 + 64 = 80
Pattern Recognition

Using parametric coordinates (at², 2at) systematically reduces algebraic complexity when determining intersections or triangle properties on a parabola.

Chapter Mix

Class 11 Maths: Conic Sections

Q9 jee_main_2026_28_january_evening Ellipse Parameters and Latus Rectum
An ellipse has its center at (1,-2), one focus at (3,-2) and one vertex at (5, - 2). Then the length of its latus rectum is :
  • A. 16√(3)
  • B. 6
  • C. 4√(3)
  • D. 6√(3)

Solution

Related Formula
Latus Rectum (LR) = (2b²)/(a) = 2a(1-e²)
Core Logic

From the given coordinates on the major axis (y = -2): Center C(1, -2), Focus F₁(3, -2), Vertex A₁(5, -2). Distance from center to vertex, CA₁ = a = 5 - 1 = 4. Distance from center to focus, CF₁ = ae = 3 - 1 = 2.

Ellipse dimensions mapped to coordinates
Ellipse dimensions mapped to coordinates

Execution

Calculate eccentricity e:

ae = 2 ⇒ 4e = 2 ⇒ e = (1)/(2)

Use alternate formula for Latus Rectum:

LR = 2e((a)/(e) - ae) or directly 2a(1-e²) LR = 2(4)(1 - (1)/(4)) = 8 × (3)/(4) = 6
Pattern Recognition

Aligning focus, center, and vertex along a constant y-axis implies a standard shifted ellipse where absolute differences in x-coordinates yield standard parameters (a and ae) directly.

Chapter Mix

Class 11 Maths: Conic Sections

Q10 jee_main_2026_28_january_evening Confocal Ellipse and Hyperbola
Let the ellipse E: x²144 + y²169 = 1 and the hyperbola H: x²16 - y²λ² = -1 have the same foci. If e and L respectively denote the eccentricity and the length of the latus rectum of H, then the value of 24(e + L) is:
  • A. 296
  • B. 126
  • C. 148
  • D. 67

Solution

Related Formula
e = √(1 - (a²)/(b²)) (for vertical ellipse) e = √(1 + (a²)/(b²)) (for conjugate hyperbola)
Core Logic

For Ellipse E: (x²)/(144) + (y²)/(169) = 1 a² = 144, b² = 169. Since b > a, the major axis is along the y-axis. Eccentricity e' = √(1 - (144)/(169)) = √((25)/(169)) = (5)/(13). Foci of ellipse = (0, ± be') = (0, ± 13 × (5)/(13)) = (0, ± 5).

Execution

For Hyperbola H: (y²)/(λ²) - (x²)/(16) = 1 Foci of conjugate hyperbola are (0, ± λ e). Equating foci: λ e = 5.

e = √(1 + (16)/(λ²)) λ √(1 + (16)/(λ²)) = 5 ⇒ λ² + 16 = 25 ⇒ λ² = 9 ⇒ λ = 3

Eccentricity of hyperbola, e = (5)/(3). Length of latus rectum of hyperbola, L = (2(16))/(λ) = (32)/(3).

Calculate 24(e + L):

24(e + L) = 24[(5)/(3) + (32)/(3)] = 24((37)/(3)) = 8 × 37 = 296
Pattern Recognition

Confocal conics usually align along the same major axis. Notice the -1 on the RHS of the hyperbola equation indicates a conjugate hyperbola orienting it vertically to match the b>a ellipse.

Chapter Mix

Class 11 Maths: Conic Sections

Q12 jee_main_2026_28_january_evening Parametric Form and Chord Intersections
Let the circle x² + y² = 4 intersect x-axis at the points A(a, 0), a > 0 and B(b, 0). Let P(2 α, 2 α), 0 < α < (π)/(2) and Q(2 β, 2 β) be two points such that (α - β) = (π)/(2). Then the point of intersection of AQ and BP lies on:
  • A. x² + y² - 4y - 4 = 0
  • B. x² + y² - 4x - 4 = 0
  • C. x² + y² - 4x - 4y = 0
  • D. x² + y² - 4x - 4y - 4 = 0

Solution

Core Logic

Intersection of circle with x-axis provides A(2,0) and B(-2,0). Let the point of intersection of AQ and BP be R(h, k). Since R lies on BP, the slope mBR = mBP:

(k)/(h + 2) = (2 α)/(2 α + 2) = (α)/(2)

Since R lies on AQ, the slope mAR = mAQ:

(k)/(h - 2) = (2 β)/(2 β - 2) = ( β)/( β - 1) = - (β)/(2)
Execution

We are given α - β = (π)/(2) ⇒ (α)/(2) - (β)/(2) = (π)/(4). Applying the (A-B) formula:

((α)/(2) - (β)/(2)) = ( (α)/(2) - (β)/(2))/(1 + (α)/(2) (β)/(2)) = 1

Substitute the slope relations: (α)/(2) = (k)/(h+2) (β)/(2) = -(h-2)/(k) (since - (β)/(2) = (k)/(h-2))

1 = ((k)/(h+2) + (h-2)/(k))/(1 + ((k)/(h+2))((2-h)/(k))) 1 = k² + h² - 4(k(h+2))/(k) · (k(h+2) - k(2-h))/(k(h+2)) wait, clear denominator 1 = (k² + h² - 4)/(k(h+2) + k(2-h)) × k(h+2) The denominator simplifies to:

1 + (2-h)/(h+2) = (h+2+2-h)/(h+2) = (4)/(h+2)

Numerator is (k² + h² - 4)/(k(h+2)). So the expression simplifies to:

1 = (k² + h² - 4)/(4k) h² + k² - 4k - 4 = 0

Locus of R is x² + y² - 4y - 4 = 0.

Pattern Recognition

Connecting chords from extreme diameter vertices to points whose parametric angles differ by π/2 reliably generates perpendicular-like slope products or standard tangent angle identities, mapping directly to a circular locus.

Chapter Mix

Class 11 Maths: Circles

Q55 jee_main_2025_02_april_evening Ellipse
If the length of the minor axis of an ellipse is equal to one fourth of the distance between the foci, then the eccentricity of the ellipse is :
  • A. 4√(17)
  • B. √(3)16
  • C. 3√(19)
  • D. √(5)7

Solution

Related Formula
Length of minor axis = 2b Distance between foci = 2ae Eccentricity: e = √(1 - (b²)/(a²))
Core Logic

We set up an algebraic equation relating b, a, and e from the given geometric condition, then substitute it into the eccentricity identity.

Step 1: Set up the geometric relation

Given that 2b = (1)/(4) (2ae):

b = (ae)/(4) (b)/(a) = (e)/(4)

Square both sides:

(b²)/(a²) = (e²)/(16)
Step 2: Solve for eccentricity

Using the eccentricity relation:

e² = 1 - (b²)/(a²) e² = 1 - (e²)/(16) e² (1 + (1)/(16)) = 1 (17)/(16) e² = 1 e² = (16)/(17) e = 4√(17)
Pattern Recognition

Standard Ellipse relations: For standard ellipses, the ratio of axes and the eccentricity are coupled quadratic equations. Expressing b/a as a function of e allows direct solving of the eccentricity.

Chapter Mix

Class 11 Mathematics: Conic Sections

Rankbit System
JEE Physics: Waves (+15.5%) | Electrostatics: Concentric Shells (-29.7%) | Modern Physics: Photoelectric Clones (+34.2%) | Mathematics: Definite Integrals (+18.1%) | Chemistry: Coordination Splitting (-11.4%) | JEE Physics: Waves (+15.5%) | Electrostatics: Concentric Shells (-29.7%) | Modern Physics: Photoelectric Clones (+34.2%) | Mathematics: Definite Integrals (+18.1%) | Chemistry: Coordination Splitting (-11.4%)