Math Problem Statement

Suppose alpha and beta are the roots of 4x^(2) -6x +3=0. Find the value of each of the following expressions without solving the equation. (alpha^(2)-beta^(2))

Solution

To solve for α2β2\alpha^2 - \beta^2 without solving the quadratic equation, we use the relationship between the roots and coefficients of the quadratic equation.

Step 1: Given equation

The quadratic equation is:

4x26x+3=04x^2 - 6x + 3 = 0

From this equation, we identify:

  • a=4a = 4
  • b=6b = -6
  • c=3c = 3

The roots α\alpha and β\beta satisfy the following relationships:

  1. Sum of roots: α+β=ba=64=32\alpha + \beta = -\frac{b}{a} = -\frac{-6}{4} = \frac{3}{2}
  2. Product of roots: αβ=ca=34\alpha \beta = \frac{c}{a} = \frac{3}{4}

Step 2: Using the difference of squares identity

The difference of squares is given by:

α2β2=(α+β)(αβ)\alpha^2 - \beta^2 = (\alpha + \beta)(\alpha - \beta)

We already know α+β=32\alpha + \beta = \frac{3}{2}. Now, to find αβ\alpha - \beta, we use the discriminant of the quadratic equation:

αβ=(α+β)24αβ\alpha - \beta = \sqrt{(\alpha + \beta)^2 - 4\alpha\beta}

Step 3: Calculating αβ\alpha - \beta

Substitute α+β=32\alpha + \beta = \frac{3}{2} and αβ=34\alpha \beta = \frac{3}{4}:

αβ=(32)24(34)\alpha - \beta = \sqrt{\left(\frac{3}{2}\right)^2 - 4\left(\frac{3}{4}\right)}

αβ=943=94124=34\alpha - \beta = \sqrt{\frac{9}{4} - 3} = \sqrt{\frac{9}{4} - \frac{12}{4}} = \sqrt{-\frac{3}{4}}

This result indicates that αβ\alpha - \beta is imaginary. Hence, α2β2\alpha^2 - \beta^2 becomes complex. Using the expression:

α2β2=(α+β)(αβ)\alpha^2 - \beta^2 = (\alpha + \beta)(\alpha - \beta)

We find:

α2β2=32i34\alpha^2 - \beta^2 = \frac{3}{2} \cdot i\sqrt{\frac{3}{4}}

α2β2=3i34\alpha^2 - \beta^2 = \frac{3i\sqrt{3}}{4}

Final Answer:

α2β2=3i34\alpha^2 - \beta^2 = \frac{3i\sqrt{3}}{4}

Let me know if you want further clarification on these steps!

Questions for deeper understanding:

  1. What is the role of the discriminant in determining if roots are real or complex?
  2. How does the difference of squares formula apply to complex numbers?
  3. Can you deduce (α+β)2+(αβ)2(\alpha + \beta)^2 + (\alpha - \beta)^2 using the same quadratic relationships?
  4. How would the solution differ if α\alpha and β\beta were real roots?
  5. Can you derive αn+βn\alpha^n + \beta^n for any integer nn using this approach?

Tip: Always examine the discriminant (b24acb^2 - 4ac) of a quadratic equation before assuming the nature of its roots!

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Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Equations
Roots and Coefficients Relationship
Complex Numbers

Formulas

Sum of roots: alpha + beta = -b/a
Product of roots: alpha * beta = c/a
Difference of squares: alpha^2 - beta^2 = (alpha + beta)(alpha - beta)

Theorems

Relationship Between Roots and Coefficients of Quadratic Equations

Suitable Grade Level

Grades 10-12