Math Problem Statement

(z+1)^3 = (\overline{z} - 2 + \sqrt{3}i)^3

Solution

Problem Analysis

We are tasked with solving the equation:

(z+1)3=(z2+3i)3(z+1)^3 = (\overline{z} - 2 + \sqrt{3}i)^3

where zz is a complex number, and z\overline{z} denotes the conjugate of zz.


Solution

  1. Introduce the polar form of the cubes:

    Since both sides are cubes, take the cube root of both sides: z+1=(z2+3i)ωkz+1 = (\overline{z} - 2 + \sqrt{3}i) \cdot \omega^k where ω=e2πi/3\omega = e^{2\pi i / 3} is a primitive cube root of unity, and k=0,1,2k = 0, 1, 2 accounts for the three cube roots.

  2. Let z=x+yiz = x + yi:

    Write zz as x+yix + yi (where x,yRx, y \in \mathbb{R}), so z=xyi\overline{z} = x - yi. Substituting into the equation: (x+1+yi)=((xyi)2+3i)ωk.(x + 1 + yi) = \left((x - yi) - 2 + \sqrt{3}i\right) \cdot \omega^k.

  3. Expand and equate real and imaginary parts:

    Expand the right-hand side: z2+3i=x2yi+3i=(x2)+(y+3)i.\overline{z} - 2 + \sqrt{3}i = x - 2 - yi + \sqrt{3}i = (x - 2) + (-y + \sqrt{3})i.

    Including ωk\omega^k, this becomes: z+1=[(x2)+(y+3)i]ωk.z + 1 = [(x - 2) + (-y + \sqrt{3})i] \cdot \omega^k.

    Separate real and imaginary parts for each kk.

  4. Solve for zz:

    Analyze each of the three cases k=0,1,2k = 0, 1, 2, accounting for both real and imaginary parts. By solving these equations, you will obtain the values of zz.


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Related Questions

  1. How do primitive cube roots of unity work in solving such equations?
  2. Can you explain how the conjugate of a complex number interacts with the polar form?
  3. How many unique solutions should we expect for this equation?
  4. How does equating real and imaginary parts help in solving complex equations?
  5. What are other scenarios where solving powers of complex equations arises?

Tip

Always remember to include all roots (e.g., ωk\omega^k) when solving polynomial equations in the complex domain!

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Math Problem Analysis

Mathematical Concepts

Complex Numbers
Cube Roots
Polar Form
Algebra

Formulas

z = x + yi
Cube Root of Unity: \omega = e^{2\pi i / 3}

Theorems

Polar form of complex numbers
Properties of cube roots of unity

Suitable Grade Level

Grades 11-12