Math Problem Statement

Let alpha, beta be the roots of the equation x^2+2√2x-1 the quadratic equation whose roots are a^4+B^4 and 1/10(a^6+B^6)is

Solution

We need to find the quadratic equation whose roots are α4+β4\alpha^4 + \beta^4 and 110(α6+β6)\frac{1}{10}(\alpha^6 + \beta^6), where α\alpha and β\beta are the roots of the equation:

x2+22x1=0x^2 + 2\sqrt{2}x - 1 = 0

Step 1: Find the roots α\alpha and β\beta

The roots α\alpha and β\beta can be found using the quadratic formula:

α,β=b±b24ac2a\alpha, \beta = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}

Here, a=1a = 1, b=22b = 2\sqrt{2}, and c=1c = -1. Plugging in these values:

α,β=22±(22)24(1)(1)2(1)\alpha, \beta = \frac{-2\sqrt{2} \pm \sqrt{(2\sqrt{2})^2 - 4(1)(-1)}}{2(1)}

α,β=22±8+42\alpha, \beta = \frac{-2\sqrt{2} \pm \sqrt{8 + 4}}{2}

α,β=22±122\alpha, \beta = \frac{-2\sqrt{2} \pm \sqrt{12}}{2}

α,β=22±232\alpha, \beta = \frac{-2\sqrt{2} \pm 2\sqrt{3}}{2}

α,β=2±3\alpha, \beta = -\sqrt{2} \pm \sqrt{3}

So the roots are:

α=2+3,β=23\alpha = -\sqrt{2} + \sqrt{3}, \quad \beta = -\sqrt{2} - \sqrt{3}

Step 2: Calculate α4+β4\alpha^4 + \beta^4

We will now compute α4+β4\alpha^4 + \beta^4.

First, note that:

α+β=22,αβ=(2)2(3)2=23=1\alpha + \beta = -2\sqrt{2}, \quad \alpha\beta = (\sqrt{2})^2 - (\sqrt{3})^2 = 2 - 3 = -1

To find α4+β4\alpha^4 + \beta^4, we use the identity:

α4+β4=(α2+β2)22α2β2\alpha^4 + \beta^4 = (\alpha^2 + \beta^2)^2 - 2\alpha^2\beta^2

First, we need α2+β2\alpha^2 + \beta^2 and α2β2\alpha^2\beta^2:

α2+β2=(α+β)22αβ=(22)22(1)=8+2=10\alpha^2 + \beta^2 = (\alpha + \beta)^2 - 2\alpha\beta = (-2\sqrt{2})^2 - 2(-1) = 8 + 2 = 10

α2β2=(αβ)2=(1)2=1\alpha^2\beta^2 = (\alpha\beta)^2 = (-1)^2 = 1

Now:

α4+β4=(10)22(1)=1002=98\alpha^4 + \beta^4 = (10)^2 - 2(1) = 100 - 2 = 98

Step 3: Calculate 110(α6+β6)\frac{1}{10}(\alpha^6 + \beta^6)

We use the identity:

α6+β6=(α2+β2)(α4+β4α2β2)\alpha^6 + \beta^6 = (\alpha^2 + \beta^2)(\alpha^4 + \beta^4 - \alpha^2\beta^2)

Using the values we computed:

α6+β6=(10)(981)=10×97=970\alpha^6 + \beta^6 = (10)(98 - 1) = 10 \times 97 = 970

Thus:

110(α6+β6)=97010=97\frac{1}{10}(\alpha^6 + \beta^6) = \frac{970}{10} = 97

Step 4: Form the new quadratic equation

The roots of the desired quadratic equation are 9898 and 9797. Therefore, the equation is:

x2(sum of roots)x+(product of roots)=0x^2 - (\text{sum of roots})x + (\text{product of roots}) = 0

The sum of the roots is 98+97=19598 + 97 = 195, and the product of the roots is 98×97=950698 \times 97 = 9506. So the quadratic equation is:

x2195x+9506=0x^2 - 195x + 9506 = 0

This is the quadratic equation whose roots are α4+β4\alpha^4 + \beta^4 and 110(α6+β6)\frac{1}{10}(\alpha^6 + \beta^6).

Would you like more details or have any questions?


  1. What is the general method for finding roots of a quadratic equation?
  2. How can we derive identities like α4+β4\alpha^4 + \beta^4 in terms of simpler expressions?
  3. Why is the quadratic equation with roots 9898 and 9797 important here?
  4. What are other identities related to symmetric sums of powers of roots?
  5. How does the choice of signs in the quadratic formula affect the roots?

Tip: When solving quadratic equations, it's important to simplify intermediate expressions carefully to avoid mistakes in calculations.

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Math Problem Analysis

Mathematical Concepts

Quadratic Equations
Roots of Equations
Symmetric Sums of Powers

Formulas

Quadratic formula
Sum and product of roots of quadratic equation

Theorems

Vieta's formulas

Suitable Grade Level

High School