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 and are the roots of the equation , then
Options
- A
- B1
- C2
- D
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)=-2 \cos \frac{2 \pi}{3}=-2\left(-\frac{1}{2}\right)=1