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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 2

Q17 jee_main_2026_23_january_evening De Moivre's Theorem
If z = √(3)2 + (i)/(2), i = √(-1), then (z²⁰¹ - i)⁸ is equal to
  • A. -1
  • B. 0
  • C. 1
  • D. 256

Solution

Related Formula
eiθ = θ + i θ (r eiθ)ⁿ = rⁿ ei(nθ)
Core Logic

Represent z in polar form:

z = √(3)2 + i(1)/(2) = ((π)/(6)) + i ((π)/(6)) = eiπ/6

Calculate z²⁰¹:

z²⁰¹ = (eiπ/6)²⁰¹ = ei(201π/6) = ei(67π/2)
Step 1: Simplify Exponent
ei(67π/2) = ((67π)/(2)) + i ((67π)/(2))

Note that (67π)/(2) = 33π + (π)/(2).

(33π + (π)/(2)) = (odd multiple of π + (π)/(2)) = 0 (33π + (π)/(2)) = - ((π)/(2)) = -1

Thus, z²⁰¹ = -i.

Step 2: Final Calculation

Substitute z²⁰¹ into the expression:

(z²⁰¹ - i)⁸ = (-i - i)⁸ = (-2i)⁸ (-2)⁸ (i)⁸ = 256 × 1 = 256
Pattern Recognition

Convert standard coordinate complex numbers into Euler form immediately when large powers are present.

Chapter Mix

Class 11 Maths: Complex Numbers

Q9 jee_main_2026_24_january_morning Locus in Complex Plane
Let S = z in C : | (z - 6i)/(z - 2i) | = 1 and | (z - 8 + 2i)/(z + 2i) | = (3)/(5). Then Σz in S |z|² is equal to
  • A. 398
  • B. 413
  • C. 423
  • D. 385

Solution

Related Formula
|z - z₁| = |z - z₂| represents the perpendicular bisector of the segment joining z₁ and z₂ |x+iy|² = x² + y²
Core Logic

First condition: |z - 6i| = |z - 2i|. This means z lies on the perpendicular bisector of (0,6) and (0,2). Let z = x + iy. Thus, y = 4.

Step 1: Circle Equation

Second condition: 5|z - 8 + 2i| = 3|z + 2i|. Substitute y = 4 into z: z = x + 4i.

5|x + 4i - 8 + 2i| = 3|x + 4i + 2i| 5|x - 8 + 6i| = 3|x + 6i|

Squaring both sides:

25((x - 8)² + 36) = 9(x² + 36) 25(x² - 16x + 64 + 36) = 9x² + 324 25x² - 400x + 2500 = 9x² + 324 16x² - 400x + 2176 = 0

Divide by 16:

x² - 25x + 136 = 0
Step 2: Roots and Modulus

Roots of x² - 25x + 136 = 0:

(x - 17)(x - 8) = 0 ⇒ x = 17 or x = 8

Thus, the points in S are z₁ = 17 + 4i and z₂ = 8 + 4i.

Σz in S |z|² = |17 + 4i|² + |8 + 4i|² = (17² + 4²) + (8² + 4²) = (289 + 16) + (64 + 16) = 305 + 80 = 385
Pattern Recognition

Whenever an absolute value ratio equals 1, immediately map it to a line (perpendicular bisector) and substitute its constraint directly into the second curve equation to reduce dimensionality.

Chapter Mix

Class 11 Maths: Complex Numbers and Quadratic Equations

Q23 jee_main_2026_24_january_evening Properties of Moduli
Let z = (1 + i)(1 + 2i)(1 + 3i) (1 + ni), where i = √(-1). If |z|² = 44200, then n is equal to
Numerical Answer. Answer: 5 to 5

Solution

Related Formula
|z₁ · z₂ zₙ| = |z₁| · |z₂| |zₙ| |1 + ri|² = 1² + r² = 1 + r²
Core Logic

Given z = Πr=1ⁿ (1 + ri). Take the modulus of both sides:

|z| = Πr=1ⁿ |1 + ri|

Square both sides:

|z|² = Πr=1ⁿ |1 + ri|² = Πr=1ⁿ (1 + r²)
Step 1: Factoring the Target Number

We are given |z|² = 44200. Factorizing 44200:

44200 = 442 × 100 = (2 × 221) × (10²) = 2 × (13 × 17) × (2² × 5²) = 2³ · 5² · 13 · 17
Step 2: Expanding the Product

Calculate the product series step-by-step for small values of n: For r=1: 1 + 1² = 2 For r=2: 1 + 2² = 5 For r=3: 1 + 3² = 10 = 2 × 5 For r=4: 1 + 4² = 17 For r=5: 1 + 5² = 26 = 2 × 13

Now, multiply these first 5 terms together:

P₅ = 2 × 5 × 10 × 17 × 26 = 2 × 5 × (2 × 5) × 17 × (2 × 13) = 2³ × 5² × 13 × 17
Step 3: Comparing and Concluding

The calculated product for n=5 exactly matches the prime factorization of 44200. Therefore, n = 5.

Pattern Recognition

Modulus is multiplicative. In problems featuring chains of complex multiplications set equal to a huge real magnitude, instantly switch to magnitudes and map to integer factorization.

Chapter Mix

Class 11 Maths: Complex Numbers

Q5 jee_main_2026_28_january_morning Geometry of Complex Numbers
Let z be a complex number such that |z - 6| = 5 and |z + 2 - 6i| = 5. Then the value of z³ + 3z² - 15z + 141 is equal to
  • A. 42
  • B. 37
  • C. 50
  • D. 61

Solution

Core Logic

Geometry of Complex Numbers
Geometry of Complex Numbers
The given equations represent two circles in the complex plane: Circle 1: Center C₁(6, 0), radius r₁ = 5 Circle 2: Center C₂(-2, 6), radius r₂ = 5

Distance between the centers C₁ and C₂:

C₁C₂ = √((-2 - 6)² + (6 - 0)²) = √(64 + 36) = 10

Notice that C₁C₂ = r₁ + r₂ = 5 + 5 = 10. This means the two circles touch each other externally at exactly one point.

Step 1: Finding z

Since the circles touch externally, the common point z is the midpoint of the line segment joining the centers C₁ and C₂.

z = (6 + (-2))/(2) + i (0 + 6)/(2)

z = 2 + 3i

Step 2: Simplifying the Polynomial

We have z = 2 + 3i. z - 2 = 3i Squaring both sides: (z - 2)² = -9

z² - 4z + 4 = -9 z² - 4z + 13 = 0

z² = 4z - 13

Step 3: Evaluating the Expression

We need to evaluate z³ + 3z² - 15z + 141. First, find z³:

z³ = z · z² = z(4z - 13) = 4z² - 13z

Substitute z² = 4z - 13 again:

z³ = 4(4z - 13) - 13z = 16z - 52 - 13z = 3z - 52

Now substitute z³ and z² into the target expression:

(3z - 52) + 3(4z - 13) - 15z + 141 = 3z - 52 + 12z - 39 - 15z + 141 = (3z + 12z - 15z) + (-52 - 39 + 141)

= 0 + 50 = 50

Pattern Recognition

When given two complex distance modulus equations |z-z₁|=r₁ and |z-z₂|=r₂, always check the distance between centers |z₁ - z₂|. If it exactly equals r₁ + r₂, the single unique solution is the section formula midpoint.

Chapter Mix

Class 11 Mathematics: Complex Numbers and Quadratic Equations

Q10 jee_main_2026_28_january_morning Nature of Roots
If α, β, where α < β, are the roots of the equation λ x² - (λ + 3)x + 3 = 0 such that (1)/(α) - (1)/(β) = (1)/(3), then the sum of all possible values of λ is:
  • A. 6
  • B. 2
  • C. 4
  • D. 8

Solution

Related Formula

For a quadratic equation ax² + bx + c = 0: Sum of roots: α + β = -(b)/(a) Product of roots: αβ = (c)/(a)

Core Logic

From the given equation λ x² - (λ + 3)x + 3 = 0:

α + β = (λ + 3)/(λ) αβ = (3)/(λ)

We are given the condition:

(1)/(α) - (1)/(β) = (1)/(3) (β - α)/(αβ) = (1)/(3) β - α = (αβ)/(3) = (3/λ)/(3) = (1)/(λ)
Step 1: Square Identity

We know that (α + β)² - 4αβ = (β - α)². Substitute the known values:

(β - α)² = (1)/(λ²) (α + β)² = ((λ + 3)²)/(λ²)

So, we substitute these into the identity:

((λ + 3)²)/(λ²) - 4((3)/(λ)) = (1)/(λ²)
Step 2: Solving for Lambda

Multiply the entire equation by λ² (assuming λ ≠ 0 because it's a quadratic leading coefficient):

(λ + 3)² - 12λ = 1 λ² + 6λ + 9 - 12λ - 1 = 0 λ² - 6λ + 8 = 0
Step 3: Finding Roots
(λ - 2)(λ - 4) = 0

So, λ = 2 or λ = 4. (The solution notes λ=0 derived from λ³ - 6λ² + 8λ = 0 by cross multiplication, but λ=0 degrades the quadratic. Thus valid λ in 2, 4). Sum of possible values of λ = 2 + 4 = 6.

Chapter Mix

Class 11 Mathematics: Complex Numbers and Quadratic Equations

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