Cube Roots Of Unity
Let omega be a non-real cube root of unity; the value of the expression (1 + omega)^3 - (1 + omega^2)^3 evaluated using the standard identities equals which number?
Select the correct option:
🔒 Solution Hidden from View
Submit your answer to unlock the detailed step-by-step solution.
More complex numbers and quadratic equations Practice Questions
The set of all complex numbers z satisfying the equation given by the ratio condition arg of the qua...
The set of all complex numbers z satisfying the equation given by the ratio condition arg of the qua...
If the equation x^2 - (k - 3)x + k = 0 has both roots real, then the set of all real values of the p...
If the equation x^2 - (k - 3)x + k = 0 has both roots real, then the set of all real values of the p...
Among all complex numbers z lying on the circle defined by |z| = 1, the maximum value attained by th...
Among all complex numbers z lying on the circle defined by |z| = 1, the maximum value attained by th...
If alpha and beta are roots of x^2 - 2x + 4 = 0, then the value of the symmetric expression alpha cu...
If alpha and beta are roots of x^2 - 2x + 4 = 0, then the value of the symmetric expression alpha cu...
The values of the real parameter m for which the quadratic equation (m + 1)x^2 + 2(m + 3)x + (m + 8)...
The values of the real parameter m for which the quadratic equation (m + 1)x^2 + 2(m + 3)x + (m + 8)...
For any complex number z, the expression z multiplied by its conjugate z-bar is always equal to whic...
For any complex number z, the expression z multiplied by its conjugate z-bar is always equal to whic...
If two complex numbers have moduli 2 and 5 and arguments 40 degrees and 80 degrees respectively, the...
If two complex numbers have moduli 2 and 5 and arguments 40 degrees and 80 degrees respectively, the...
If the two quadratic equations x^2 + bx + c = 0 and x^2 + cx + b = 0, with b not equal to c, share e...
If the two quadratic equations x^2 + bx + c = 0 and x^2 + cx + b = 0, with b not equal to c, share e...
For all real x, the quadratic expression f(x) = x^2 - 6x + 11 attains a minimum value, and that mini...
For all real x, the quadratic expression f(x) = x^2 - 6x + 11 attains a minimum value, and that mini...
If alpha and beta are the roots of x^2 - 4x + 1 = 0, then the quadratic equation whose roots are the...
If alpha and beta are the roots of x^2 - 4x + 1 = 0, then the quadratic equation whose roots are the...
If one root of the real-coefficient quadratic x^2 + px + q = 0 is the complex number 2 + 3i, then th...
If one root of the real-coefficient quadratic x^2 + px + q = 0 is the complex number 2 + 3i, then th...
For a complex number z satisfying the constraint |z - 4| ≤ 3, the maximum possible value of the modu...
For a complex number z satisfying the constraint |z - 4| ≤ 3, the maximum possible value of the modu...
Browse all complex numbers and quadratic equations questions →
About This Question
- Subject
- mathematics
- Chapter
- complex numbers and quadratic equations
- Topic
- cube roots of unity
- Difficulty
- Medium
- Year
- 2025
Solution
Correct Answer:
0
The non-real cube roots of unity satisfy 1 + omega + omega^2 = 0 and omega^3 = 1, identities that drive most JEE Advanced complex-number simplifications. From the first identity, 1 + omega = -omega^2 and 1 + omega^2 = -omega. Therefore (1 + omega)^3 = (-omega^2)^3 = -omega^6 = -(omega^3)^2 = -1, and (1 + omega^2)^3 = (-omega)^3 = -omega^3 = -1. The required difference is (-1) - (-1) = 0. The symmetry between omega and omega^2 makes the two cubes equal, forcing the difference to vanish. Option 2 ignores that both cubes equal -1. Option -2 reverses a sign incorrectly. Option 1 drops a factor. Hence the expression equals 0. Plausibility check: since omega and omega^2 are complex conjugates, the two bracketed terms are conjugates, and cubing preserves conjugacy; their difference is twice the imaginary part of a real number, which is zero, confirming the result. The cube roots of unity sit at the vertices of an equilateral triangle inscribed in the unit circle, so their geometric symmetry mirrors the algebraic relation that their sum vanishes. Exploiting omega and omega squared as a conjugate pair, and repeatedly reducing powers using omega cubed equal to one, collapses a wide variety of intimidating expressions to small real numbers with very little computation.
This medium difficulty mathematics question is from the chapter complex numbers and quadratic equations, covering the topic of cube roots of unity. It appeared in the 2025 exam.
Looking for more practice? Explore all mathematics questions or browse complex numbers and quadratic equations questions on RankGuru.