JEE Main · Mathematics ↓ Falling

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

Year 2026 2025 2024 Total
Questions 11 16 14 41

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 Type:
Enter a numerical value Answer: 49 to 49 +4 marks

Solution & Explanation

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

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_2026_22_january_morning

Practice all Complex Numbers previous-year questions →

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