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Let alpha, beta be the roots of the equa...

Let `alpha, beta` be the roots of the equation `x^2 +2 sqrt 2x-1 = 0`. The quadratic equation, whose roots are `alpha^(4) + beta^(4)` and `1/(10)(alpha^6 + beta^6)`, is:

A

`x^2 - 180x + 9506 = 0`

B

`x^2 - 190x + 9466 = 0`

C

`x^2 - 195x + 9466 = 0`

D

`x^2 - 195x + 9506 = 0`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to follow these steps: ### Step 1: Find the roots of the equation The given quadratic equation is: \[ x^2 + 2\sqrt{2}x - 1 = 0 \] Using the quadratic formula \( x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \), where \( a = 1, b = 2\sqrt{2}, c = -1 \): - Calculate the discriminant: \[ b^2 - 4ac = (2\sqrt{2})^2 - 4(1)(-1) = 8 + 4 = 12 \] - Now, substituting into the quadratic formula: \[ x = \frac{-2\sqrt{2} \pm \sqrt{12}}{2} = \frac{-2\sqrt{2} \pm 2\sqrt{3}}{2} = -\sqrt{2} \pm \sqrt{3} \] Thus, the roots are: \[ \alpha = -\sqrt{2} + \sqrt{3}, \quad \beta = -\sqrt{2} - \sqrt{3} \] ### Step 2: Calculate \( \alpha^2 + \beta^2 \) Using the identity: \[ \alpha^2 + \beta^2 = (\alpha + \beta)^2 - 2\alpha\beta \] We know: - \( \alpha + \beta = -2\sqrt{2} \) - \( \alpha \beta = -1 \) Now, substituting these values: \[ \alpha^2 + \beta^2 = (-2\sqrt{2})^2 - 2(-1) = 8 + 2 = 10 \] ### Step 3: Calculate \( \alpha^4 + \beta^4 \) Using the identity: \[ \alpha^4 + \beta^4 = (\alpha^2 + \beta^2)^2 - 2(\alpha\beta)^2 \] Substituting the values: \[ \alpha^4 + \beta^4 = 10^2 - 2(-1)^2 = 100 - 2 = 98 \] ### Step 4: Calculate \( \alpha^6 + \beta^6 \) Using the identity: \[ \alpha^6 + \beta^6 = (\alpha^2 + \beta^2)(\alpha^4 + \beta^4) - \alpha^2\beta^2(\alpha^2 + \beta^2) \] Substituting the known values: - \( \alpha^2 + \beta^2 = 10 \) - \( \alpha^4 + \beta^4 = 98 \) - \( \alpha \beta = -1 \) implies \( \alpha^2 \beta^2 = 1 \) Now substituting: \[ \alpha^6 + \beta^6 = 10 \times 98 - 1 \times 10 = 980 - 10 = 970 \] ### Step 5: Find the second root \( \frac{1}{10}(\alpha^6 + \beta^6) \) Calculating: \[ \frac{1}{10}(\alpha^6 + \beta^6) = \frac{970}{10} = 97 \] ### Step 6: Form the quadratic equation The roots of the new quadratic equation are \( \alpha^4 + \beta^4 = 98 \) and \( \frac{1}{10}(\alpha^6 + \beta^6) = 97 \). The sum of the roots: \[ 98 + 97 = 195 \] The product of the roots: \[ 98 \times 97 = 9506 \] Thus, the quadratic equation is: \[ x^2 - (sum \ of \ roots)x + (product \ of \ roots) = 0 \] \[ x^2 - 195x + 9506 = 0 \] ### Final Answer The quadratic equation is: \[ x^2 - 195x + 9506 = 0 \] ---
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