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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 positive

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To find the values of \( \alpha \) for which both roots of the quadratic equation \( 4x^2 - 4(\alpha - 2)x + \alpha - 2 = 0 \) are positive, we will follow these steps: ### Step 1: Identify the coefficients The given quadratic equation can be expressed in the standard form \( ax^2 + bx + c = 0 \), where: - \( a = 4 \) - \( b = -4(\alpha - 2) = -4\alpha + 8 \) - \( c = \alpha - 2 \) ### Step 2: Ensure the discriminant is non-negative For the quadratic equation to have real roots, the discriminant \( D \) must be greater than or equal to zero. The discriminant is given by: \[ D = b^2 - 4ac \] Substituting the values of \( a \), \( b \), and \( c \): \[ D = (-4\alpha + 8)^2 - 4(4)(\alpha - 2) \] Calculating \( D \): \[ D = (16\alpha^2 - 64\alpha + 64) - 16(\alpha - 2) \] \[ D = 16\alpha^2 - 64\alpha + 64 - 16\alpha + 32 \] \[ D = 16\alpha^2 - 80\alpha + 96 \] Setting the discriminant \( D \geq 0 \): \[ 16\alpha^2 - 80\alpha + 96 \geq 0 \] Dividing the entire inequality by 16: \[ \alpha^2 - 5\alpha + 6 \geq 0 \] ### Step 3: Factor the quadratic Factoring the quadratic: \[ (\alpha - 2)(\alpha - 3) \geq 0 \] The roots of the equation are \( \alpha = 2 \) and \( \alpha = 3 \). ### Step 4: Analyze the sign of the quadratic Using a number line to test the intervals: - For \( \alpha < 2 \): Both factors are negative, so the product is positive. - For \( 2 < \alpha < 3 \): One factor is positive, and the other is negative, so the product is negative. - For \( \alpha > 3 \): Both factors are positive, so the product is positive. Thus, the solution to the inequality is: \[ \alpha \leq 2 \quad \text{or} \quad \alpha \geq 3 \] ### Step 5: Ensure both roots are positive For both roots to be positive, we also need to check the condition: \[ -\frac{b}{2a} > 0 \] Calculating: \[ -\frac{-4(\alpha - 2)}{2 \cdot 4} > 0 \] \[ \frac{4(\alpha - 2)}{8} > 0 \] \[ \alpha - 2 > 0 \implies \alpha > 2 \] ### Step 6: Combine conditions From the conditions: 1. \( \alpha \leq 2 \) or \( \alpha \geq 3 \) 2. \( \alpha > 2 \) The valid range for \( \alpha \) is: \[ \alpha \geq 3 \] ### Final Answer The values of \( \alpha \) for which both roots are positive are: \[ \alpha \in [3, \infty) \]
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FIITJEE-QUADRATIC EQUATION & EXPRESSION -ASSIGNMENT PROBLEMS (SUBJECTIVE) Level - II
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