Math Problem Statement

If α,β are the roots of equation x²-2x+3=0, then find 1/(2-α)⁴+1/(2-β)⁴ ?

Solution

We are given that α\alpha and β\beta are the roots of the quadratic equation:

x22x+3=0.x^2 - 2x + 3 = 0.

To solve for α\alpha and β\beta, we can use the quadratic formula:

x=b±b24ac2a,x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}, where a=1a = 1, b=2b = -2, and c=3c = 3.

Substitute the values of aa, bb, and cc into the formula:

x=(2)±(2)24(1)(3)2(1)=2±4122=2±82.x = \frac{-(-2) \pm \sqrt{(-2)^2 - 4(1)(3)}}{2(1)} = \frac{2 \pm \sqrt{4 - 12}}{2} = \frac{2 \pm \sqrt{-8}}{2}.

Since 8=2i2\sqrt{-8} = 2i\sqrt{2}, we have:

x=2±2i22=1±i2.x = \frac{2 \pm 2i\sqrt{2}}{2} = 1 \pm i\sqrt{2}.

Thus, the roots are α=1+i2\alpha = 1 + i\sqrt{2} and β=1i2\beta = 1 - i\sqrt{2}.

Step 1: Find 1(2α)4+1(2β)4\frac{1}{(2 - \alpha)^4} + \frac{1}{(2 - \beta)^4}

We need to find:

1(2α)4+1(2β)4.\frac{1}{(2 - \alpha)^4} + \frac{1}{(2 - \beta)^4}.

First, simplify 2α2 - \alpha and 2β2 - \beta:

2α=2(1+i2)=1i2,2 - \alpha = 2 - (1 + i\sqrt{2}) = 1 - i\sqrt{2}, 2β=2(1i2)=1+i2.2 - \beta = 2 - (1 - i\sqrt{2}) = 1 + i\sqrt{2}.

Now, calculate (2α)4(2 - \alpha)^4 and (2β)4(2 - \beta)^4. Since 2α=2β2 - \alpha = \overline{2 - \beta}, the two terms are conjugates.

Let z=1i2z = 1 - i\sqrt{2}. Then:

(2α)4=z4,(2β)4=z4.(2 - \alpha)^4 = z^4, \quad (2 - \beta)^4 = \overline{z}^4.

Using De Moivre's theorem, we calculate the fourth power of a complex number. Express zz in polar form:

z=1i2z=12+(2)2=3.z = 1 - i\sqrt{2} \quad \Rightarrow \quad |z| = \sqrt{1^2 + (\sqrt{2})^2} = \sqrt{3}.

The argument θ\theta is given by:

θ=tan1(21).\theta = \tan^{-1}\left(\frac{-\sqrt{2}}{1}\right).

Thus, z4z^4 will have magnitude z4=32=9|z|^4 = 3^2 = 9 and argument 4θ4\theta.

Since z4z^4 and z4\overline{z}^4 have the same magnitude, both terms yield the same result, and:

1(2α)4+1(2β)4=281.\frac{1}{(2 - \alpha)^4} + \frac{1}{(2 - \beta)^4} = \frac{2}{81}.

The final answer is:

281.\boxed{\frac{2}{81}}.

Would you like further details or have any questions?

Here are 5 related questions to expand your understanding:

  1. How does the quadratic formula apply to finding complex roots?
  2. What is De Moivre's theorem, and how is it used with powers of complex numbers?
  3. Can you derive the polar form of a complex number from its rectangular form?
  4. How do you calculate the magnitude and argument of a complex number?
  5. What are the properties of complex conjugates and how do they simplify calculations?

Tip: When dealing with complex numbers, using polar form simplifies raising them to powers or finding roots.

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Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Equations
Complex Numbers
De Moivre's Theorem

Formulas

Quadratic formula: x = (-b ± √(b² - 4ac)) / 2a
Polar form of complex numbers
De Moivre's Theorem: (cos θ + i sin θ)^n = cos(nθ) + i sin(nθ)

Theorems

Quadratic Formula
De Moivre's Theorem

Suitable Grade Level

Grades 11-12