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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
Both the roots are greater than `(1)/(2)`

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To solve the quadratic equation \(4x^2 - 4(\alpha - 2)x + (\alpha - 2) = 0\) for the values of \(\alpha\) such that both roots are greater than \(\frac{1}{2}\), we will follow these steps: ### Step 1: Ensure the roots are real For the roots of the quadratic equation to be real, the discriminant \(D\) must be non-negative. The discriminant for the given quadratic equation is given by: \[ D = b^2 - 4ac \] Here, \(a = 4\), \(b = -4(\alpha - 2)\), and \(c = \alpha - 2\). Calculating the discriminant: \[ D = [-4(\alpha - 2)]^2 - 4 \cdot 4 \cdot (\alpha - 2) \] \[ D = 16(\alpha - 2)^2 - 16(\alpha - 2) \] Factoring out \(16(\alpha - 2)\): \[ D = 16(\alpha - 2)[(\alpha - 2) - 1] = 16(\alpha - 2)(\alpha - 3) \] Setting the discriminant \(D \geq 0\): \[ 16(\alpha - 2)(\alpha - 3) \geq 0 \] This gives us two critical points: \(\alpha = 2\) and \(\alpha = 3\). Analyzing the sign of the expression, we find: - The expression is positive when \(\alpha < 2\) or \(\alpha > 3\). ### Step 2: Ensure both roots are greater than \(\frac{1}{2}\) For both roots to be greater than \(\frac{1}{2}\), we can use the condition that the value of the quadratic function at \(x = \frac{1}{2}\) must be positive (since the parabola opens upwards). Calculating \(f\left(\frac{1}{2}\right)\): \[ f\left(\frac{1}{2}\right) = 4\left(\frac{1}{2}\right)^2 - 4(\alpha - 2)\left(\frac{1}{2}\right) + (\alpha - 2) \] \[ = 4 \cdot \frac{1}{4} - 2(\alpha - 2) + (\alpha - 2) \] \[ = 1 - 2\alpha + 4 + \alpha - 2 \] \[ = 3 - \alpha \] Setting this greater than zero: \[ 3 - \alpha > 0 \implies \alpha < 3 \] ### Step 3: Combine the conditions From Step 1, we have \(\alpha < 2\) or \(\alpha > 3\). From Step 2, we have \(\alpha < 3\). Combining these conditions, we find that the only valid range for \(\alpha\) is: \[ \alpha < 2 \] Thus, the values of \(\alpha\) for which both roots of the quadratic equation are greater than \(\frac{1}{2}\) are: \[ \alpha \in (-\infty, 2) \]
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FIITJEE-QUADRATIC EQUATION & EXPRESSION -ASSIGNMENT PROBLEMS (SUBJECTIVE) Level - II
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