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Let 4x^(2)-4(alpha-2)x + alpha-2=0(alpha...

Let `4x^(2)-4(alpha-2)x + alpha-2=0(alpha in R)` be a quadratic equation. Find the values of `alpha` for which
Exactly one root lies in `(0, (1)/(2))`

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To solve the problem, we need to find the values of \( \alpha \) for which exactly one root of the quadratic equation \( 4x^2 - 4(\alpha-2)x + \alpha-2 = 0 \) lies in the interval \( (0, \frac{1}{2}) \). ### Step 1: Identify the quadratic equation The given quadratic equation is: \[ 4x^2 - 4(\alpha - 2)x + (\alpha - 2) = 0 \] ### Step 2: Determine the conditions for the roots For a quadratic equation \( ax^2 + bx + c = 0 \) to have real and distinct roots, the discriminant \( D \) must be greater than zero: \[ D = b^2 - 4ac > 0 \] Here, \( a = 4 \), \( b = -4(\alpha - 2) \), and \( c = \alpha - 2 \). ### Step 3: Calculate the discriminant Calculating the discriminant: \[ D = [-4(\alpha - 2)]^2 - 4 \cdot 4 \cdot (\alpha - 2) \] \[ = 16(\alpha - 2)^2 - 16(\alpha - 2) \] \[ = 16[(\alpha - 2)^2 - (\alpha - 2)] \] \[ = 16(\alpha - 2)(\alpha - 3) \] For the roots to be real and distinct, we need: \[ 16(\alpha - 2)(\alpha - 3) > 0 \] This simplifies to: \[ (\alpha - 2)(\alpha - 3) > 0 \] ### Step 4: Solve the inequality The critical points are \( \alpha = 2 \) and \( \alpha = 3 \). We analyze the sign of the product in the intervals: 1. \( \alpha < 2 \) : Both factors are negative, so the product is positive. 2. \( 2 < \alpha < 3 \) : One factor is positive and the other is negative, so the product is negative. 3. \( \alpha > 3 \) : Both factors are positive, so the product is positive. Thus, the solution to the inequality is: \[ \alpha < 2 \quad \text{or} \quad \alpha > 3 \] ### Step 5: Check the condition for root in the interval (0, 1/2) We need to ensure that exactly one root lies in the interval \( (0, \frac{1}{2}) \). 1. **Evaluate \( f(0) \)**: \[ f(0) = \alpha - 2 \] For \( f(0) > 0 \) (the quadratic opens upwards), we need: \[ \alpha - 2 > 0 \implies \alpha > 2 \] 2. **Evaluate \( f\left(\frac{1}{2}\right) \)**: \[ f\left(\frac{1}{2}\right) = 4\left(\frac{1}{2}\right)^2 - 4(\alpha - 2)\left(\frac{1}{2}\right) + (\alpha - 2) \] \[ = 1 - 2(\alpha - 2) + (\alpha - 2) \] \[ = 1 - 2\alpha + 4 + \alpha - 2 \] \[ = 3 - \alpha \] For \( f\left(\frac{1}{2}\right) < 0 \): \[ 3 - \alpha < 0 \implies \alpha > 3 \] ### Step 6: Combine the conditions From the conditions derived: 1. \( \alpha < 2 \) or \( \alpha > 3 \) (for distinct roots) 2. \( \alpha > 3 \) (for one root in \( (0, \frac{1}{2}) \)) The only valid solution is: \[ \alpha > 3 \] ### Final Answer The values of \( \alpha \) for which exactly one root lies in \( (0, \frac{1}{2}) \) are: \[ \alpha > 3 \]
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FIITJEE-QUADRATIC EQUATION & EXPRESSION -ASSIGNMENT PROBLEMS (SUBJECTIVE) Level - II
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  2. Let 4x^(2)-4(alpha-2)x + alpha-2=0(alpha in R) be a quadratic equation...

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