Cube Roots of Unity diagram for Q21 - JEE Main 2026 Morning
Pattern Recognition
Complex expressions with ω$\omega$ raised to large powers almost always exploit rotational symmetry. If coefficients are permuted circularly (A, B, C) → (C, A, B) → (B, C, A)$(A, B, C) \to (C, A, B) \to (B, C, A)$, multiplying by ω$\omega$ maps them to one another, meaning their sum of 3n$3n$ or symmetric powers identically nullifies.
Keywords:#complex roots#JEE Main 2026 Morning Q21#Complex Numbers JEE Main 2026#Cube Roots of Unity JEE Main 2026
More Complex Numbers Previous-Year Questions — Page 7
Q21jee_main_2024_29_january_eveningRoots of Quadratic Equations
Let α, β$\alpha, \beta$ be the roots of the equation x² - √(6) x + 3 = 0$x^2 - \sqrt{6} x + 3 = 0$ such that Im(α) > Im(β)$\operatorname{Im}(\alpha) > \operatorname{Im}(\beta)$. Let a, b$a, b$ be integers not divisible by 3 and n$n$ be a natural number such that α⁹⁹β + α⁹⁸ = 3ⁿ (a + ib), i = √(-1)$\frac{\alpha^{99}}{\beta} + \alpha^{98} = 3^n (a + ib), i = \sqrt{-1}$. Then n + a + b$n + a + b$ is equal to
Numerical Answer.Answer: 49 to 49
Solution
Related Formula
Using Euler's formula:
eiθ = θ + i θ$$e^{i\theta} = \cos\theta + i\sin\theta$$
Core Logic
Solving the quadratic root configurations for x² - √(6)x + 3 = 0$x^2 - \sqrt{6}x + 3 = 0$:
Comparing with the given expression 3ⁿ(a + ib)$3^n(a + ib)$:
n = 49, a = -1, b = 1$$n = 49, \quad a = -1, \quad b = 1$$
Therefore:
n + a + b = 49 - 1 + 1 = 49$$n + a + b = 49 - 1 + 1 = 49$$
Pattern Recognition
Convert complex expressions into polar form r eiθ$r e^{i\theta}$ early. Power scaling like α⁹⁸$\alpha^{98}$ becomes simple multiplication under Euler structures.
Chapter Mix
Class 11 Mathematics: Complex Numbers and Quadratic Equations
Let the set C = (x,y) x² -2y = 2023, x,yin N$C = \left\{(x,y)\mid x^2 -2^{y} = 2023, x,y\in \mathbb{N}\right\}$. Then Σ(x,y)in C(x + y)$\sum_{(x,y)\in C}(x + y)$ is equal to
Numerical Answer.Answer: 46 to 46
Solution
Related Formula
Analyze structural equations through modular constraints (e.g., modulo 3 or 4) to limit potential bounds.
Core Logic
Given the equation: x² - 2^y = 2023$x^2 - 2^y = 2023$.
Let us inspect the numbers modulo 8:
2023 ≡ 7 8$$2023 \equiv 7 \pmod 8$$
A perfect square x²$x^2$ can only be congruent to 0, 1, 4 8$0, 1, 4 \pmod 8$.
If y ≥ 3$y \geq 3$, then 2^y ≡ 0 8 x² ≡ 7 8$2^y \equiv 0 \pmod 8 \implies x^2 \equiv 7 \pmod 8$, which is impossible.
Therefore, y$y$ must be less than 3. Since y in N$y \in \mathbb{N}$, the only choices are y = 1$y = 1$ or y = 2$y = 2$.
Exponential Diophantine equations (equations with variables in exponents) are best analyzed using modular arithmetic constraints to quickly find small finite upper bounds.
Chapter Mix
Class 11 Mathematics: Principle of Mathematical Induction / Number Theory
Qjee_main_2024_27_jan_morningModulus and Conjugate
If S=zin C:|z-i|=|z+i|=|z-1|$S=\{z\in C:|z-i|=|z+i|=|z-1|\}$, then n(S)$n(S)$ is:
A.1$1$
B.0$0$
C.3$3$
D.2$2$
Solution
Related Formula
|z - z₁| = |z - z₂|$$|z - z_1| = |z - z_2|$$
This represents the perpendicular bisector of the line segment joining the points z₁$z_1$ and z₂$z_2$ in the complex plane.
Core Logic
The given set defines a complex number z$z$ that is equidistant from three fixed points:
A ≡ (0, 1)$A \equiv (0, 1)$ corresponding to i$i$B ≡ (0, -1)$B \equiv (0, -1)$ corresponding to -i$-i$C ≡ (1, 0)$C \equiv (1, 0)$ corresponding to 1$1$
The condition |z-i|=|z+i|=|z-1|$|z-i|=|z+i|=|z-1|$ implies that z$z$ is the point of intersection of the perpendicular bisectors of the sides of the triangle formed by A$A$, B$B$, and C$C$.
Step 1: Finding the Circumcenter
The point of intersection of the perpendicular bisectors of a triangle is its circumcenter.
Since A(0,1)$A(0,1)$, B(0,-1)$B(0,-1)$, and C(1,0)$C(1,0)$ form a unique, non-degenerate triangle, they have exactly one unique circumcenter.
Step 2: Final Conclusion
Therefore, there is only one such complex number z$z$ that satisfies the condition.
n(S) = 1$n(S) = 1$
Pattern Recognition
Recognize that |z - z₁| = |z - z₂| = |z - z₃|$|z - z_1| = |z - z_2| = |z - z_3|$ is geometrically identical to finding the circumcenter of a triangle with vertices at z₁$z_1$, z₂$z_2$, and z₃$z_3$. A non-collinear set of three points always yields exactly 1 circumcenter.
Chapter Mix
Class 11 Maths: Complex Numbers
Class 11 Maths: Straight Lines
Q30jee_main_2024_27_jan_morningCube Roots of Unity
If α$\alpha$satisfies the equationx²+x+1=0$x^{2}+x+1=0$ and (1+α)⁷=A+Bα+Cα²$(1+\alpha)^{7}=A+B\alpha+C\alpha^{2}$, A, B, C≥ 0$A, B, C\ge 0$, then 5(3A-2B-C)$5(3A-2B-C)$ is equal to:
Numerical Answer.Answer: 5 to 5
Solution
Related Formula
1 + ω + ω² = 0$$1 + \omega + \omega^2 = 0$$
ω³ = 1$\omega^3 = 1$
Core Logic
The equation x² + x + 1 = 0$x^2 + x + 1 = 0$ is the standard identity whose roots are the non-real cube roots of unity, ω$\omega$ and ω²$\omega^2$.
Let us assign α = ω$\alpha = \omega$.
We are given the expression (1+α)⁷$(1+\alpha)^7$.
Substituting the root: (1+ω)⁷$(1+\omega)^7$.
Step 1: Simplify using Unity Properties
From the identity 1 + ω + ω² = 0$1 + \omega + \omega^2 = 0$, we extract:
We compare 1 + α$1 + \alpha$ with A + Bα + Cα²$A + B\alpha + C\alpha^2$.
Notice that 1 + α$1 + \alpha$ can be directly represented without any α²$\alpha^2$ term (and we must keep A, B, C ≥ 0$\ge 0$).
So, A = 1$A = 1$, B = 1$B = 1$, C = 0$C = 0$.
Step 4: Final Output Evaluation
Substitute these constants into the required equation 5(3A - 2B - C)$5(3A - 2B - C)$:
The roots of x²+x+1=0$x^2+x+1=0$ are always ω, ω²$\omega, \omega^2$. Expressions of the form (1+ω)^k$(1+\omega)^k$ rapidly collapse down to single variables via the 1+ω+ω²=0$1+\omega+\omega^2=0$ rule, making multi-variable polynomial equations instantly trivial.
Chapter Mix
Class 11 Maths: Complex Numbers
Q5jee_main_2024_29_jan_morningModulus and Equality of Complex Numbers
If z=(1)/(2)-2i$z=\frac{1}{2}-2i$, is such that |z+1|=α z+β(1+i)$|z+1|=\alpha z+\beta(1+i)$, i=√(-1)$i=\sqrt{-1}$ and α,βin R$\alpha,\beta\in R$, then α+β$\alpha+\beta$ is equal to
Equating complex parts reduces single complex equations into two simultaneous linear equations. Treat |z+1|$|z+1|$ strictly as a scalar magnitude and parse directly into algebraic components.
Chapter Mix
Class 11 Mathematics: Complex Numbers and Quadratic Equations
More Complex Numbers Questions — jee_main_2026_22_january_morning
Practice past-year questions one chapter at a time. Pick an exam → subject → chapter and get every PYQ for that topic — pulled together from all past papers — with the chapter's key formulas alongside.