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JEE Main 2010
Exam
JEE Main
Year
2010
Subject
Mathematics
Chapter
Quadratic Equation

JEE Main 2010 · Mathematics · Quadratic Equation

If α and β are the roots of the equation x^2-x+1=0 , then α^ 2009...

If α\alpha and β\beta are the roots of the equation x2−x+1=0x^2-x+1=0, then α2009+β2009=\alpha^{2009}+\beta^{2009}=

Options

  1. A−1-1
  2. B1
  3. C2
  4. D−2-2

Correct answer

B. 1

Step-by-step solution

x^2-x+1=0 \quad \Rightarrow x=\frac{1 \pm \sqrt{1-4}}{2} x=\frac{1 \pm \sqrt{3} i}{2} \alpha=\frac{1}{2}+i \frac{\sqrt{3}}{2}, \quad \beta=\frac{1}{2}-\frac{i \sqrt{3}}{2} \alpha=\cos \frac{\pi}{3}+i \sin \frac{\pi}{3}, \quad \beta=\cos \frac{\pi}{3}-i \sin \frac{\pi}{3} \alpha^{2009}+\beta^{2009}=2 \cos 2009\left(\frac{\pi}{3}\right)=2cos⁡[668π+π+2π3]=2cos⁡(π+2π3)=2 \cos \left[668 \pi+\pi+\frac{2 \pi}{3}\right]=2 \cos \left(\pi+\frac{2 \pi}{3}\right)=-2 \cos \frac{2 \pi}{3}=-2\left(-\frac{1}{2}\right)=1
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