JEE Main · Mathematics ↓ Falling

Complex Numbers appeared 41 times across 3 years — 4.7% of Mathematics. This question is from Geometry of Complex Numbers.

Year 2026 2025 2024 Total
Questions 11 16 14 41

Let P=zin C:|z+2-3i|≤1 and Q=zin C:z(1+i)+ z(1-i)≤-8. Let in P Q, |z-3+2i| be maximum and minimum at z₁ and z₂ respectively. If |z₁|²+2|z₂|²=α+β√(2), where α, β are integers, then α+β equals

Numerical Answer Type:
Enter a numerical value Answer: 36 to 36 +4 marks

Solution & Explanation

Related Formula

For a complex coordinate transformation, substituting z = x + iy and its conjugate z = x - iy maps a complex condition directly into rectangular Cartesian coordinates.

Core Logic

Let's translate the complex set properties into Cartesian geometry:

  • Set P: |z - (-2 + 3i)| ≤ 1 Interior and boundary of a circle with center C(-2, 3) and radius r = 1.
  • Set Q: (x+iy)(1+i) + (x-iy)(1-i) ≤ -8 (x - y + ix + iy) + (x - y - ix - iy) ≤ -8
2(x - y) ≤ -8 x - y + 4 ≤ 0

This defines a half-plane below or to the left of the boundary line L₂: x - y + 4 = 0.

Step 1: Identify Extreme Points for Distance from Point A

We want to find points in the region P Q that minimize and maximize the distance to the external point A(3, -2), corresponding to |z - (3 - 2i)|.

The line L₁ connecting center C(-2, 3) and point A(3, -2) has slope:

m = (-2 - 3)/(3 - (-2)) = (-5)/(5) = -1

Equation of line L₁: y - 3 = -1(x + 2) x + y - 1 = 0.

Geometric region intersection for complex inequalities for Q27 - JEE Main 2024 01 February Morning
The graphic details the intersection region bounded by the circular locus and the line inequality, showing points z1 and z2 relative to external reference point P.

Step 2: Calculate Coordinates for z₁ and z₂
  • Minimum Distance Point (z₂): By geometric observation, the minimum distance from A to the bounded region is the intersection point of lines L₁ and L₂:
x - y + 4 = 0 and x + y - 1 = 0 2x + 3 = 0 x = -(3)/(2), y = (5)/(2)

So, z₂ = (-(3)/(2), (5)/(2)).

  • Maximum Distance Point (z₁): The maximum distance is at the far boundary edge of the circle along line L₁. The vector path from C(-2, 3) opposite to A has unit direction (- 1√(2), 1√(2)):
z₁ = (-2 - 1√(2), 3 + 1√(2))
Step 3: Evaluate Magnitudes and Sum Parameters

Calculate the squares of the moduli:

|z₁|² = (-2 - 1√(2))² + (3 + 1√(2))² = 4 + 2√(2) + (1)/(2) + 9 + 3√(2) + (1)/(2) = 14 + 5√(2) |z₂|² = (-(3)/(2))² + ((5)/(2))² = (9)/(4) + (25)/(4) = (34)/(4) = (17)/(2)

Now compute the total requested term:

|z₁|² + 2|z₂|² = (14 + 5√(2)) + 2((17)/(2)) = 14 + 5√(2) + 17 = 31 + 5√(2)

Matching with α + β√(2) gives α = 31 and β = 5. Thus:

α + β = 31 + 5 = 36
Pattern Recognition

Sees: Locus intersection involving geometric complex inequalities. Shortcut: Translating complex equations into standard 2D graphs reveals the geometry instantly, mapping extreme distances to line intersections or boundary nodes cleanly.

Chapter Mix

Class 11 Complex Numbers: Geometry Class 11 Coordinate Geometry: Straight Lines

More Complex Numbers Previous-Year Questions — Page 9

Q26 jee_main_2024_31_jan_morning Properties of Modulus and Argument
If α denotes the number of solutions of |1 - i|^x = 2^x and β = ((|z|)/( (z))), where z = (π)/(4) (1 + i)⁴ ( 1 - √(π) i√(π) + i + √(π) - i1 + √(π) i), i = √(-1), then the distance of the point (α, β) from the line 4x - 3y = 7 is
Numerical Answer. Answer: 3 to 3

Solution

Core Logic
|1 - i|^x = 2^x (√(2))^x = 2^x 2x/2 = 2^x

This implies (x)/(2) = x x = 0. There is exactly 1 solution, so α = 1.

Step 1: Simplify complex number z
(1+i)⁴ = ((1+i)²)² = (1 + i² + 2i)² = (2i)² = -4

Thus, z = -π ( (1-√(π)i)(√(π)-i)π + 1 + (√(π)-i)(1-√(π)i)1 + π )

Step 2: Simplify Bracket

Let's expand the terms directly: z = (π)/(4)(-4) [ √(π) - π i - i - √(π)π + 1 + √(π) - i - π i - √(π)1 + π ]

= -π [ (-i(π+1))/(π+1) + (-i(π+1))/(π+1) ] = -π [ -i - i ] = 2π i
Step 3: Find beta

For z = 2π i: |z| = 2π and (z) = (π)/(2).

β = (|z|)/( (z)) = (2π)/(π/2) = 4
Step 4: Distance from Line

Distance of point (α, β) = (1, 4) from the line 4x - 3y - 7 = 0:

D = |4(1) - 3(4) - 7|√(4² + (-3)²) = (|4 - 12 - 7|)/(5) = (|-15|)/(5) = 3
Chapter Mix

Class 11 Maths: Complex Numbers and Quadratic Equations Class 11 Maths: Straight Lines

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