Roots Transformation D07A52
1. **Problem:** Find an equation whose roots are $a^3\beta$ and $\alpha\beta^3$, where $a$ and $\beta$ are roots of $2x^2 - 4x + 1 = 0$.
2. **Step 1: Identify sum and product of roots of the original equation.**
The quadratic is $2x^2 - 4x + 1 = 0$.
Sum of roots $a + \beta = -\frac{-4}{2} = 2$.
Product of roots $a\beta = \frac{1}{2}$.
3. **Step 2: Find sum and product of new roots $a^3\beta$ and $a\beta^3$.**
Sum:
$$a^3\beta + a\beta^3 = a\beta(a^2 + \beta^2)$$
Recall $a^2 + \beta^2 = (a + \beta)^2 - 2a\beta = 2^2 - 2 \times \frac{1}{2} = 4 - 1 = 3$$
So sum = $a\beta \times 3 = \frac{1}{2} \times 3 = \frac{3}{2}$.
Product:
$$a^3\beta \times a\beta^3 = a^4 \beta^4 = (a\beta)^4 = \left(\frac{1}{2}\right)^4 = \frac{1}{16}$$
4. **Step 3: Form the quadratic equation with roots $a^3\beta$ and $a\beta^3$.**
Using sum and product of roots, the quadratic is:
$$x^2 - \left(\text{sum}\right)x + \text{product} = 0$$
$$x^2 - \frac{3}{2}x + \frac{1}{16} = 0$$
5. **Step 4: Clear denominators for a nicer form.**
Multiply entire equation by 16:
$$16x^2 - 24x + 1 = 0$$
**Final answer:**
$$16x^2 - 24x + 1 = 0$$
This is the quadratic equation whose roots are $a^3\beta$ and $a\beta^3$.