Let $\alpha, \beta$ be the roots of the equation $x^2+2 \sqrt{2} x-1=0$. The quadratic equation, whose roots are $\alpha^4+\beta^4$ and $\frac{1}{10}(\alpha^6+\beta^6)$, is:
Solution
<p>$$\begin{aligned}
& x^2+2 \sqrt{2 x}-1=0 \\
& \alpha+\beta=-2 \sqrt{2} \text { and } \alpha \beta=-1 \\
& \alpha^2+\beta^2=(\alpha+\beta)^2-2 \alpha \beta \\
& =8+2=10 \\
& \alpha^4+\beta^4=\left(\alpha^2+\beta^2\right)^2-2(\alpha \beta)^2 \\
& =100-2=98 \\
& \alpha^6+\beta^6=\left(\alpha^2+\beta^2\right)^3-3 \alpha^2 \beta^2\left(\alpha^2+\beta^2\right) \\
& =1000-3(10) \\
& =970 \\
& \therefore \quad \frac{1}{10}\left(\alpha^6+\beta^6\right)=97
\end{aligned}$$</p>
<p>Equation whose roots are $\alpha^4+\beta^4$ and $\frac{1}{10}\left(\alpha^6+\beta^6\right)$ is</p>
<p>$$\begin{aligned}
& x^2-(98+97) x+98 \times 97=0 \\
& x^2-195 x+9506=0
\end{aligned}$$</p>
About this question
Subject: Mathematics · Chapter: Complex Numbers and Quadratic Equations · Topic: Complex Numbers and Argand Plane
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