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 A = z in C : |z - 2 - i| = 3, B = z in C : Re(z - iz) = 2 and S = A B. Then Σz in S |z|² is equal to

Numerical Answer Type:
Enter a numerical value Answer: 22 to 22 +4 marks

Solution & Explanation

Related Formula

Magnitude squared representation:

|z|² = x² + y² for z = x + iy
Core Logic

Convert complex sets into Cartesian forms by setting z = x + iy: Set A: |(x-2) + i(y-1)| = 3 (x-2)² + (y-1)² = 9 (1) Set B: z - iz = (x+iy) - i(x+iy) = (x+y) + i(y-x). Re(z - iz) = 2 x + y = 2 y = 2 - x (2)

Step 1: Solve System Algebraically

Substitute (2) into (1):

(x - 2)² + (2 - x - 1)² = 9 (x - 2)² + (1 - x)² = 9 x² - 4x + 4 + 1 - 2x + x² = 9 2x² - 6x - 4 = 0 x² - 3x - 2 = 0

Roots are x1,2 = 3 ± √(17)2. Correspondingly, y = 2 - x y1,2 = 1 ∓ √(17)2.

Step 2: Evaluate Sum of Square Magnitudes

Since S consists of the two intersection points z₁, z₂:

Σz in S |z|² = (x₁² + y₁²) + (x₂² + y₂²) = (x₁² + x₂²) + (y₁² + y₂²)

Using identities from quadratic equation x² - 3x - 2 = 0 (x₁+x₂ = 3, x₁x₂ = -2): x₁² + x₂² = (3)² - 2(-2) = 13. Since y = 2-x, y² = 4 - 4x + x² y₁² + y₂² = 8 - 4(3) + 13 = 9.

Σz in S |z|² = 13 + 9 = 22
Pattern Recognition

Avoid explicitly using radical root approximations. Summing symmetric expressions directly through standard Vieta coefficient sum shortcuts preserves clean fractions.

Chapter Mix

Class 11 Mathematics: Complex Numbers and Quadratic Equations

Reference Study Guides

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

More Complex Numbers Questions — jee_main_2025_04_april_morning

Practice all Complex Numbers previous-year questions →

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