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

Q17 jee_main_2026_21_jan_morning Cube Roots of Unity
If x² + x + 1 = 0 , then the value of (x+ 1x)⁴+(x²+ 1x²)⁴+(x³+ 1x³)⁴+…+(x²⁵+ 1x²⁵)⁴ is :
  • A. 128
  • B. 162
  • C. 175
  • D. 145

Solution

Related Formula
x² + x + 1 = 0 ⇒ x = ω, ω²

Properties of cube roots of unity: ω³ = 1 and 1 + ω + ω² = 0.

Core Logic

Let α = ω. Then (1)/(x) = (1)/(ω) = ω². The series is Σk=1²⁵ (ω^k + ω2k)⁴. Evaluate the term Tk = (ω^k + ω2k)⁴ based on the modulo of k with 3.

Step 1: Cyclic Evaluation

Case 1: k = 3m (multiples of 3)

T3m = (ω3m + ω6m)⁴ = (1 + 1)⁴ = 2⁴ = 16

There are 8 such multiples up to 25 (3, 6, 9, , 24).

Case 2: k ≠ 3m (non-multiples of 3) For k = 1, 2, 4, 5, ω^k + ω2k will always be ω + ω² or ω² + ω. Since 1 + ω + ω² = 0, we have ω + ω² = -1.

Tk ≠ 3m = (-1)⁴ = 1

There are 25 - 8 = 17 such non-multiples up to 25.

Step 2: Total Sum
Sum = 17 × 1 + 8 × 16 = 17 + 128 = 145
Pattern Recognition

Powers of x+1/x when x solves x² ± x + 1 = 0 perfectly orbit around periods of 3 or 6. Isolate the 3m resonant beats (which hit pure scalars like 1+1=2) versus the out-of-phase beats (which collapse to -1 or 1 via basic ω identities).

Chapter Mix

Class 11 Maths: Complex Numbers and Quadratic Equations

Q19 jee_main_2026_21_jan_evening Geometry of Complex Numbers
Let z be the complex number satisfying |z-5|≤ 3 and having maximum positive principal argument. Then 34|(5z-12)/(5iz+16)|² is equal to:
  • A. 16
  • B. 12
  • C. 26
  • D. 20

Solution

Related Formula
For maximum argument of z on a circle, the ray from origin is tangent to the circle. If |z-a| ≤ r, maximum argument implies θ = (r)/(|a|) and coordinates are x=a ²θ, y=a θ θ
Core Logic

Complex geometry maximum argument diagram for Q19 - JEE Main 2026 Evening
Complex geometry maximum argument diagram for Q19 - JEE Main 2026 Evening
The condition |z-5|≤ 3 represents a disk centered at (5,0) with radius 3. To maximize the principal argument θ, the ray from origin must touch the circle in the first quadrant. The tangent, origin, and center form a right-angled triangle.

Step 1: Locate the Point z

From geometry, hypotenuse c = 5, opposite (radius) r = 3. The adjacent side (length of tangent) is √(5² - 3²) = 4. The angle of tangency θ satisfies θ = (3)/(5) and θ = (4)/(5). The point P(z) lies on the circle and the tangent ray:

z ≡ (4 θ, 4 θ) = (4((4)/(5)), 4((3)/(5))) = ((16)/(5), (12)/(5)) z = (16)/(5) + (12)/(5)i
Step 2: Evaluate the Target Expression

We need 34|(5z - 12)/(5iz + 16)|². Substitute 5z = 16 + 12i: Numerator: 5z - 12 = 16 + 12i - 12 = 4 + 12i Denominator: 5iz + 16 = i(16 + 12i) + 16 = 16i - 12 + 16 = 4 + 16i Expression:

34 |(4 + 12i)/(4 + 16i)|² = 34 (|4 + 12i|²)/(|4 + 16i|²) = 34 (4² + 12²)/(4² + 16²) = 34 ((16 + 144)/(16 + 256)) = 34 ((160)/(272)) = (34 × 160)/(272) = (5440)/(272) = 20
Pattern Recognition

For maximum (z) on |z-c| = r where c is real, z coordinates are given by geometric projection: z = √(c²-r²)( θ + i θ) where θ = r/c.

Chapter Mix

Class 11 Maths: Complex Numbers

Q21 jee_main_2026_22_january_morning Cube Roots of Unity
Let α = -1 + i√(3)2 and β = -1 - i√(3)2,i = √(-1). If (7 - 7α +9β)²⁰ + (9 + 7α -7β)²⁰ + (-7 + 9α +7β)²⁰ + (14 + 7α +7β)²⁰ = m¹⁰, then m is ____.
Numerical Answer. Answer: 49 to 49

Solution

Related Formula
α = ω, β = ω² 1 + ω + ω² = 0 ω³ = 1
Core Logic

Substitute ω and ω² into the terms:

Let T₁ = 7 - 7ω + 9ω² Let T₂ = 9 + 7ω - 7ω² Let T₃ = -7 + 9ω + 7ω² Let T₄ = 14 + 7ω + 7ω²

Step 1: Simplify Each Term Using Properties of Omega

Notice relationships between the terms by factoring powers of ω:

T₁ = ω · ω²(7 - 7ω + 9ω²) wait, an easier path is factoring

Observe that:

ω · T₂ = ω(9 + 7ω - 7ω²) = 9ω + 7ω² - 7 = T₃ ω² · T₂ = ω²(9 + 7ω - 7ω²) = 9ω² + 7 - 7ω = T₁

So, T₁²⁰ + T₂²⁰ + T₃²⁰ = (ω² T₂)²⁰ + T₂²⁰ + (ω T₂)²⁰

= ω⁴⁰ T₂²⁰ + T₂²⁰ + ω²⁰ T₂²⁰ = T₂²⁰ (1 + ω⁴⁰ + ω²⁰)

Since ω³ = 1, we have ω⁴⁰ = ω and ω²⁰ = ω².

Thus, T₂²⁰ (1 + ω + ω²) = T₂²⁰ (0) = 0.

Step 2: Evaluating the Non-Zero Term

The only remaining term is T₄²⁰:

T₄ = 14 + 7(ω + ω²)

Since ω + ω² = -1,

T₄ = 14 + 7(-1) = 14 - 7 = 7

So the entire expression sum is 0 + 7²⁰ = 7²⁰.

Step 3: Finding m

Given that the sum equals m¹⁰:

m¹⁰ = 7²⁰ = (7²)¹⁰ = 49¹⁰

Hence, m = 49.

Cube Roots of Unity diagram for Q21 - JEE Main 2026 Morning
Cube Roots of Unity diagram for Q21 - JEE Main 2026 Morning

Pattern Recognition

Complex expressions with ω raised to large powers almost always exploit rotational symmetry. If coefficients are permuted circularly (A, B, C) → (C, A, B) → (B, C, A), multiplying by ω maps them to one another, meaning their sum of 3n or symmetric powers identically nullifies.

Chapter Mix

Class 11 Maths: Complex Numbers

Q4 jee_main_2026_22_january_evening Complex Equations and Modulus
Let S = z in C : 4z² + z = 0. Then Σz in S |z|² is equal to:
  • A. (3)/(16)
  • B. (7)/(64)
  • C. (1)/(16)
  • D. (5)/(64)

Solution

Related Formula

For z = x + iy, z = x - iy and |z|² = x² + y².

Core Logic

Substitute z = x + iy into 4z² + z = 0:

4(x² - y² + 2ixy) + x - iy = 0

Separating real and imaginary parts:

4x² - 4y² + x = 0 and y(8x - 1) = 0

Case 1: y = 0 4x² + x = 0 x = 0 or x = -1/4. Solutions: z₁ = 0 |z₁|² = 0, z₂ = -1/4 |z₂|² = 1/16.

Case 2: x = 1/8 4(1/64) - 4y² + 1/8 = 0 4y² = 3/16 y = ± √(3)8. Solutions: z₃, z₄ = (1)/(8) ± i √(3)8 |z₃|² = |z₄|² = (1)/(64) + (3)/(64) = (1)/(16).

Step 1: Sum of Modulus Squared
Σz in S |z|² = 0 + (1)/(16) + (1)/(16) + (1)/(16) = (3)/(16)
Pattern Recognition

Separate complex equation into real and imaginary components to systematically find all roots.

Chapter Mix

Class 11 Maths: Complex Numbers

Q17 jee_main_2026_23_january_morning Geometry of Complex Numbers
Let S = z : 3 ≤ |2z - 3(1 + i)| ≤ 7 be a set of complex numbers. Then z in S | ( z + (1)/(2)(5 + 3i) ) | is equal to:
  • A. (1)/(2)
  • B. (3)/(2)
  • C. 2
  • D. (5)/(2)

Solution

Core Logic

Simplify the condition for set S:

3 ≤ |2(z - (3)/(2)(1 + i))| ≤ 7 (3)/(2) ≤ |z - (3)/(2)(1 + i)| ≤ (7)/(2)

This represents an annular region bounded by two concentric circles centered at C = (3)/(2) + (3)/(2)i with radii r₁ = (3)/(2) and r₂ = (7)/(2).

Geometry of Complex Numbers diagram for Q17 - JEE Main 2026 Morning
Geometry of Complex Numbers diagram for Q17 - JEE Main 2026 Morning

Step 1: Identify the Target Point

We need to minimize | z - ( -(5)/(2) - (3)/(2)i ) |. Let P be the point -(5)/(2) - (3)/(2)i. The expression represents the distance from point P to a point z in the set S.

Step 2: Distance from Center to P

Calculate the distance PC between the center of the circles C((3)/(2), (3)/(2)) and the point P(-(5)/(2), -(3)/(2)):

PC = √(( (3)/(2) - (-(5)/(2)) )² + ( (3)/(2) - (-(3)/(2)) )²) PC = √(( (8)/(2) )² + ( (6)/(2) )²) = √(4² + 3²) = √(16 + 9) = √(25) = 5

Since 5 > (7)/(2), the point P lies outside the outer circle.

Step 3: Minimum Distance Calculation

The shortest distance from an external point to an annular region is the distance to the outer boundary along the line connecting the point to the center.

z in S |z - P| = PC - router Minimum Distance = 5 - (7)/(2) = (10 - 7)/(2) = (3)/(2)
Pattern Recognition

Transforming |az - b| by factoring out a immediately reveals the true geometric center. Shortest distance to any ring/circle from an external point is always collinear with the center: d - Router.

Chapter Mix

Class 11 Maths: Complex Numbers and Quadratic Equations

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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%)