Math Problem Statement

If α, β are the roots of 2x² - 3x - 6 = 0, then the equation whose roots are α² + 2, β² + 2 is:

Solution

The problem states that if α\alpha and β\beta are the roots of the quadratic equation:

2x23x6=02x^2 - 3x - 6 = 0

we need to find the equation whose roots are α2+2\alpha^2 + 2 and β2+2\beta^2 + 2.

Step 1: Use Vieta's Formulas

From Vieta’s formulas for a quadratic equation ax2+bx+c=0ax^2 + bx + c = 0, we know the following relationships:

  • Sum of the roots α+β=coefficient of xcoefficient of x2=(3)2=32\alpha + \beta = -\frac{\text{coefficient of } x}{\text{coefficient of } x^2} = \frac{-(-3)}{2} = \frac{3}{2}
  • Product of the roots αβ=constant termcoefficient of x2=62=3\alpha \beta = \frac{\text{constant term}}{\text{coefficient of } x^2} = \frac{-6}{2} = -3

Step 2: Find New Roots

We now need the roots of the new equation where the roots are α2+2\alpha^2 + 2 and β2+2\beta^2 + 2.

  • The sum of the new roots is: (α2+2)+(β2+2)=α2+β2+4(\alpha^2 + 2) + (\beta^2 + 2) = \alpha^2 + \beta^2 + 4

Using the identity α2+β2=(α+β)22αβ\alpha^2 + \beta^2 = (\alpha + \beta)^2 - 2\alpha \beta, we get: α2+β2=(32)22(3)=94+6=334\alpha^2 + \beta^2 = \left( \frac{3}{2} \right)^2 - 2(-3) = \frac{9}{4} + 6 = \frac{33}{4}

Thus, the sum of the new roots is: 334+4=494\frac{33}{4} + 4 = \frac{49}{4}

  • The product of the new roots is: (α2+2)(β2+2)=α2β2+2α2+2β2+4(\alpha^2 + 2)(\beta^2 + 2) = \alpha^2 \beta^2 + 2\alpha^2 + 2\beta^2 + 4

Since α2β2=(αβ)2=(3)2=9\alpha^2 \beta^2 = (\alpha \beta)^2 = (-3)^2 = 9, and α2+β2=334\alpha^2 + \beta^2 = \frac{33}{4}, the product becomes: 9+2×334+4=9+664+4=13+664=11849 + 2 \times \frac{33}{4} + 4 = 9 + \frac{66}{4} + 4 = 13 + \frac{66}{4} = \frac{118}{4}

Step 3: Form the Equation

The quadratic equation whose roots have a sum of 494\frac{49}{4} and a product of 1184\frac{118}{4} is given by:

4x249x+118=04x^2 - 49x + 118 = 0

This matches option 4 in the provided choices.


Would you like more details on any step? Here are some follow-up questions to explore this topic further:

  1. How does Vieta’s formula help in solving quadratic problems?
  2. Can you derive the sum and product of new roots for transformed equations in general?
  3. What is the significance of the identity α2+β2=(α+β)22αβ\alpha^2 + \beta^2 = (\alpha + \beta)^2 - 2\alpha\beta?
  4. How would the process change if we were solving for cubics or higher degree polynomials?
  5. What techniques can be used to verify the solution for transformed roots?

Tip: When working with quadratic equations, always try to simplify the process using identities like Vieta’s relations to avoid solving the equation from scratch.

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Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Equations
Vieta's Formulas

Formulas

Quadratic equation formula ax² + bx + c = 0
Sum of roots: α + β = -b/a
Product of roots: αβ = c/a
Identity: α² + β² = (α + β)² - 2αβ

Theorems

Vieta's Formulas

Suitable Grade Level

Grades 10-12