Equation of two diameters of a circle are 2x-3y=5 and 3x-4y=7. The line joining the points (-(22)/(7),-4) and (-(1)/(7),3) intersects the circle at only one point P(α,β). Then 17β-α is equal to

Numerical Answer Type:
Enter a numerical value Answer: 2 to 2 +4 marks

Solution & Explanation

Related Formula

The intersection of any two non-parallel diameters yields the center of the circle. A line that intersects a circle at exactly one point is a tangent line. The tangent at the point of contact P is always perpendicular to the radius CP, thus mtangent × mradius = -1.

Core Logic

Find the center C by solving the two diameter equations:

2x - 3y = 5 (1) 3x - 4y = 7 (2)

Multiply (1) by 3 and (2) by 2: 6x - 9y = 15 6x - 8y = 14 Subtracting the equations gives -y = 1 ⇒ y = -1. Substitute y = -1 into (1): 2x + 3 = 5 ⇒ 2x = 2 ⇒ x = 1. Center C is (1, -1).

Find the equation of the line joining A(-(22)/(7), -4) and B(-(1)/(7), 3). Slope of AB: mAB = (3 - (-4))/(-1/7 - (-22/7)) = (7)/(21/7) = (7)/(3). Equation of line AB:

y - 3 = (7)/(3)(x + (1)/(7))

3y - 9 = 7x + 1

7x - 3y + 10 = 0 (Line AB)

Tangents and Normal
Tangents and Normal

Step 1: Exploit Tangency Geometry

Since line AB intersects the circle at only one point P(α, β), line AB is a tangent to the circle, and P is the point of tangency. The radius line CP is perpendicular to tangent AB. Slope of CP (mCP) must be -(3)/(7).

Equation of the line passing through center C(1, -1) with slope -(3)/(7):

y - (-1) = -(3)/(7)(x - 1) 7y + 7 = -3x + 3 3x + 7y + 4 = 0 (Line CP)
Step 2: Solve for Intersection P

Point P(α, β) is the intersection of Tangent AB and Radius CP. Solve the system:

7x - 3y = -10 (× 7) 3x + 7y = -4 (× 3)

49x - 21y = -70 9x + 21y = -12 Add them: 58x = -82 ⇒ x = -(82)/(58) = -(41)/(29). So, α = -(41)/(29).

Substitute x into 3x + 7y = -4:

3(-(41)/(29)) + 7y = -4 -(123)/(29) + 7y = -(116)/(29)

7y = (123 - 116)/(29) = (7)/(29) ⇒ y = (1)/(29)$. So, $β = (1)/(29)$.

Step 3: Evaluate Target Expression

Evaluate $17β - α$:

17\left(\frac{1}{29}\right) - \left(-\frac{41}{29}\right) = \frac{17 + 41}{29} = \frac{58}{29} = 2$$
Pattern Recognition

When a line "intersects a circle at exactly one point", it's a coded cue to stop thinking about quadratics and discriminants, and immediately build a perpendicular geometric radius from the center to find the exact tangency coordinate.

Chapter Mix

Class 11 Mathematics: Circles Class 11 Mathematics: Straight Lines

Reference Study Guides

More Circles Previous-Year Questions — Page 9

Q jee_main_2025_07_april_morning Tangent and Normal to a Circle
Let C₁ be the circle in the third quadrant of radius 3, that touches both coordinate axes. Let C₂ be the circle with centre (1, 3) that touches C₁ externally at the point (α, β). If (β - α)² = (m)/(n), (m, n) = 1, then m + n is equal to:
  • A. 9
  • B. 13
  • C. 22
  • D. 31

Solution

Related Formula

For a circle in the third quadrant touching both coordinate axes, the center layout is (-r, -r) and equation looks like:

(x + r)² + (y + r)² = r²

For external contact between circles C₁ and C₂, the distance between centers equals the sum of their radii:

C₁C₂ = r₁ + r₂
Core Logic

Circle C₁ has radius r₁ = 3 and touches both axes in the third quadrant, so its center is A(-3, -3). Circle C₂ has center B(1, 3).

The distance between centers A and B is:

AB = √((1 - (-3))² + (3 - (-3))²) = √(4² + 6²) = √(16 + 36) = √(52) = 2√(13)
Step 1: Determine Radius of Circle 2

Tangent and Normal to a Circle diagram for Q59 - JEE Main 2025 Morning
Tangent and Normal to a Circle diagram for Q59 - JEE Main 2025 Morning
Since the circles touch externally:

AB = r₁ + r₂ 2√(13) = 3 + r₂ r₂ = 2√(13) - 3
Step 2: Locate the Contact Point via Section Formula

The point of contact P(α, β) divides the line segment joining centers A(-3, -3) and B(1, 3) internally in the ratio r₁ : r₂ = 3 : (2√(13) - 3).

Using the internal section formula:

α = 3(1) + (2√(13) - 3)(-3)3 + (2√(13) - 3) = 3 - 6√(13) + 92√(13) = 12 - 6√(13) + 02√(13) = 6 - 3√(13)√(13) β = 3(3) + (2√(13) - 3)(-3)3 + (2√(13) - 3) = 9 - 6√(13) + 92√(13) = 18 - 6√(13)2√(13) = 9 - 3√(13)√(13)
Step 3: Calculate the Difference Value

Find (β - α)²:

β - α = 9 - 3√(13)√(13) - 6 - 3√(13)√(13) = 3√(13) (β - α)² = ( 3√(13))² = (9)/(13)

Comparing with (m)/(n) where (m, n) = 1 gives m = 9, n = 13.

m + n = 9 + 13 = 22
Pattern Recognition

Notice that computing (β - α) directly cancels out the irrational √(13) term from the numerator before squaring, saving a significant amount of tedious arithmetic expansion.

Chapter Mix

Class 11 Mathematics: Coordinate Geometry Class 11 Mathematics: Circles

Q73 jee_main_2025_07_april_morning Hyperbola
Consider the hyperbola (x²)/(a²) -(y²)/(b²) = 1 having one of its focus at P(-3,0) . If the latus rectum through its other focus subtends a right angle at P and a² b² = α √(2) -β ,α ,β in N , calculate α + β.
Numerical Answer. Answer: 1944 to 1944

Solution

Related Formula

For a standard hyperbola:

  • Focus positions are (± ae, 0).
  • Length of semi-latus rectum is (b²)/(a).
  • Eccentricity identity linkage: b² = a²(e² - 1) a²e² = a² + b².
Core Logic

Given focus F₁ ≡ (-ae, 0) ≡ P(-3, 0), so ae = 3. The other focus is F₂ ≡ (ae, 0) ≡ (3, 0).

The latus rectum passes vertically through F₂, with endpoints L₁(ae, (b²)/(a)) and L₂(ae, -(b²)/(a)). This segment subtends a right angle at P(-ae, 0). By symmetry, the top half angle at P must be exactly 45^°.

Step 1: Set Up Slope Relationship

Hyperbola diagram for Q73 - JEE Main 2025 Morning
Hyperbola diagram for Q73 - JEE Main 2025 Morning
Using the geometric slope relationship:

45^° = heightbase = (b²/a)/(2ae) 1 = (b²)/(2a²e) 2a²e = b² b² = 6a (since ae = 3)
Step 2: Solve the Quadratic Excentricity Equation

Substitute ae = 3 and b² = 6a into the eccentricity identity a²e² = a² + b²:

9 = a² + 6a a² + 6a - 9 = 0

Solving for a using the quadratic formula (taking the positive root since a > 0):

a = -6 ± √(36 - 4(1)(-9))2 = -6 + √(72)2 = -3 + 3√(2) = 3(√(2) - 1)
Step 3: Evaluate product and sum coefficients

Now compute a²b²:

a²b² = a²(6a) = 6a³ 6a³ = 6[3(√(2) - 1)]³ = 6 × 27 × (√(2) - 1)³ 6a³ = 162 × (2√(2) - 6 + 3√(2) - 1) = 162 × (5√(2) - 7) 6a³ = 810√(2) - 1134

Matching with α√(2) - β gives:

α = 810 and β = 1134

Calculate the final required sum:

α + β = 810 + 1134 = 1944
Pattern Recognition

Recognizing that the right angle subtended at the opposite focus implies a perfect (45^°) right triangle instantly yields the key linear constraint b² = 2a(ae), avoiding the need for lengthy distance-formula tracking.

Chapter Mix

Class 11 Mathematics: Conic Sections

Q60 jee_main_2025_08_april_evening Ellipse and Focal Distances
Let the ellipse 3x² + py² = 4 pass through the centre C of the circle x² + y² - 2x - 4y - 11 = 0 of radius r. Let f₁, f₂ be the focal distances of the point C on the ellipse. Then 6f₁f₂ - r is equal to
  • A. 74
  • B. 68
  • C. 70
  • D. 78

Solution

Related Formula
Focal Distance Product on Vertical Ellipse = b² - e² k²
Core Logic

Extract the coordinate center of the target circle, substitute it directly to locate the missing parameter p, and resolve eccentricity metrics.

Step 1: Extract Circle Metric Values

For circle x² + y² - 2x - 4y - 11 = 0:

Centre C(1, 2), Radius r = √(1 + 4 + 11) = 4
Step 2: Standardize Ellipse Formulation

Ellipse passes through point C(1,2):

3(1)² + p(2)² = 4 3 + 4p = 4 p = (1)/(4)

Standard model form: (x²)/(4/3) + (y²)/(16) = 1 (b > a, vertical configuration axis).

e = √(1 - (4/3)/(16)) = √(1 - (1)/(12)) = √((11)/(12))
Step 3: Evaluate Product Chain

Focal distance elements at ordinate coordinate height k=2 are bounded by b ± ek:

f₁ f₂ = b² - e² k² = 16 - ((11)/(12)) × 4 = 16 - (11)/(3) = (37)/(3)

Target evaluation expression response string:

6f₁ f₂ - r = 6 ((37)/(3)) - 4 = 74 - 4 = 70
Pattern Recognition

Pay attention to whether b > a or a > b when analyzing ellipse forms. Focal distance definitions swap directions immediately across major horizontal/vertical configurations.

Chapter Mix

Class 11 Mathematics: Conic Sections Class 11 Mathematics: Circles

Q75 jee_main_2025_08_april_evening Tangent to Parabola and Circle Properties
Let r be the radius of the circle, which touches x -axis at point (a, 0) , a < 0 and the parabola y² = 9x at the point (4, 6) . Then r is equal to
Numerical Answer. Answer: 30 to 30

Solution

Related Formula
Tangent line at point (x₁, y₁) yy₁ = 2a(x+x₁)
Core Logic

Establish the tangent vector expression at the parabola intersection mark. Since this path line functions as a shared contact tangent boundaries sheet for the circular arc, impose radius equations.

Step 1: Derive Shared Parabola Tangent Line

Tangent line profile for y² = 9x at coordinate indicator (4,6):

6y = 9 · ( (x+4)/(2) ) 3x - 4y + 12 = 0
Step 2: Build Geometric Metric Connections

Circle touches axis at (a,0), mapping coordinates center directly to C(a,r). Perpendicular boundary constraint steps require:

(3a - 4r + 12)/(5) = ± r 3a + 12 = 4r ± 5r
Step 3: Solve for Radius Matrix Bounds

Enforce circle equation intersection constraint profile (x-a)² + (y-r)² = r² at point (4,6):

a² - 8a - 12r + 52 = 0

Evaluating the target systems from structural logic tracks rejects positive value parameters, providing:

a = -14, r = 30

{{SOL_IMG_75}}

Pattern Recognition

Shared tangent elements connect independent conic fields. Locating circular center boundaries using axial coordinate tracking simplifies secondary equations.

Chapter Mix

Class 11 Mathematics: Conic Sections Class 11 Mathematics: Circles

Q59 jee_main_2025_29_jan_evening Chord with a Given Midpoint
If α x + β y = 109 is the equation of the chord of the ellipse (x²)/(9) +(y²)/(4) = 1, whose mid point is ((5)/(2),(1)/(2)), then α +β is equal to
  • A. 37
  • B. 46
  • C. 58
  • D. 72

Solution

Related Formula

Equation of a chord of a conic section with a given midpoint (x₁, y₁) is:

T = S₁

Core Logic

Given midpoint M((5)/(2), (1)/(2)) and ellipse (x²)/(9) + (y²)/(4) = 1.

Chord with a Given Midpoint diagram for Q59 - JEE Main 2025 Evening
Chord with a Given Midpoint diagram for Q59 - JEE Main 2025 Evening

Write T and S₁ terms:

T: (x((5)/(2)))/(9) + (y((1)/(2)))/(4) S₁: (((5)/(2))²)/(9) + (((1)/(2))²)/(4)

Equating both sides:

(5x)/(18) + (y)/(8) = (25)/(36) + (1)/(16)
Step 1: Simplify to Standard Form

Multiply the entire equation by 144 to eliminate fractions:

144((5x)/(18)) + 144((y)/(8)) = 144((25)/(36)) + 144((1)/(16)) 40x + 18y = 4(25) + 9(1)

40x + 18y = 109

Comparing this directly with α x + β y = 109 provides:

α = 40, β = 18 α + β = 40 + 18 = 58
Pattern Recognition

Whenever you see 'chord whose midpoint is given', write T = S₁ automatically. Match coefficients directly at the final step after equating constant integers.

Chapter Mix

Class 11 Mathematics: Conic Sections

More Circles Questions — jee_main_2024_29_jan_morning

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