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Consider the following the next two item...

Consider the following the next two items that follow : Let `alpha and beta` be the roots of the equation `x^(2) - (1 - 2a^(2)) x + (1 - 2a^(2)) = 0`
Under what condition equation have real roots?

A

`a^(2) lt (1)/(2)`

B

`a^(2) gt (1)/(2)`

C

`a^(2) gt 1`

D

`a^(2) epsilon ((1)/(3),(1)/(2))`

Text Solution

AI Generated Solution

The correct Answer is:
To determine the condition under which the quadratic equation \( x^2 - (1 - 2a^2)x + (1 - 2a^2) = 0 \) has real roots, we need to analyze its discriminant. ### Step-by-Step Solution: 1. **Identify the coefficients**: The given quadratic equation is in the standard form \( ax^2 + bx + c = 0 \). Here, we can identify: - \( a = 1 \) - \( b = -(1 - 2a^2) \) - \( c = 1 - 2a^2 \) 2. **Write the discriminant formula**: The discriminant \( D \) of a quadratic equation \( ax^2 + bx + c = 0 \) is given by: \[ D = b^2 - 4ac \] For the roots to be real, we need \( D \geq 0 \). 3. **Calculate the discriminant**: Substitute the values of \( a \), \( b \), and \( c \) into the discriminant formula: \[ D = [-(1 - 2a^2)]^2 - 4(1)(1 - 2a^2) \] Simplifying this gives: \[ D = (1 - 2a^2)^2 - 4(1 - 2a^2) \] 4. **Expand the expression**: Now, expand \( (1 - 2a^2)^2 \): \[ D = (1 - 4a^2 + 4a^4) - (4 - 8a^2) \] This simplifies to: \[ D = 1 - 4a^2 + 4a^4 - 4 + 8a^2 \] Combining like terms results in: \[ D = 4a^4 + 4a^2 - 3 \] 5. **Set the discriminant greater than or equal to zero**: For the roots to be real, we need: \[ 4a^4 + 4a^2 - 3 \geq 0 \] 6. **Let \( t = a^2 \)**: Substitute \( t \) for \( a^2 \): \[ 4t^2 + 4t - 3 \geq 0 \] 7. **Factor the quadratic**: To solve \( 4t^2 + 4t - 3 = 0 \), we can use the quadratic formula: \[ t = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \] Here, \( a = 4 \), \( b = 4 \), and \( c = -3 \): \[ t = \frac{-4 \pm \sqrt{4^2 - 4 \cdot 4 \cdot (-3)}}{2 \cdot 4} \] \[ t = \frac{-4 \pm \sqrt{16 + 48}}{8} \] \[ t = \frac{-4 \pm \sqrt{64}}{8} \] \[ t = \frac{-4 \pm 8}{8} \] This gives us: \[ t = \frac{4}{8} = \frac{1}{2} \quad \text{and} \quad t = \frac{-12}{8} = -\frac{3}{2} \] Since \( t = a^2 \) must be non-negative, we discard \( t = -\frac{3}{2} \). 8. **Determine the intervals**: The quadratic \( 4t^2 + 4t - 3 \) opens upwards (since the coefficient of \( t^2 \) is positive). The roots are \( t = \frac{1}{2} \). The quadratic will be non-negative outside the interval defined by the roots: \[ t \leq -\frac{3}{2} \quad \text{or} \quad t \geq \frac{1}{2} \] Since \( t = a^2 \geq 0 \), we conclude: \[ a^2 \geq \frac{1}{2} \] ### Final Condition: Thus, the condition for the quadratic equation to have real roots is: \[ a^2 \geq \frac{1}{2} \]
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