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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 smaller than `(1)/(2)`

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To solve the quadratic equation \(4x^2 - 4(\alpha - 2)x + \alpha - 2 = 0\) and find the values of \(\alpha\) for which both roots are smaller than \(\frac{1}{2}\), we will follow these steps: ### Step 1: Identify the coefficients The given quadratic equation can be rewritten in standard form \(ax^2 + bx + c = 0\), where: - \(a = 4\) - \(b = -4(\alpha - 2) = -4\alpha + 8\) - \(c = \alpha - 2\) ### Step 2: Condition for real roots For the roots to be real, the discriminant \(D\) must be non-negative: \[ D = b^2 - 4ac \geq 0 \] Calculating the discriminant: \[ D = (-4\alpha + 8)^2 - 4 \cdot 4 \cdot (\alpha - 2) \] Expanding this: \[ D = (16\alpha^2 - 64\alpha + 64) - 16(\alpha - 2) \] \[ D = 16\alpha^2 - 64\alpha + 64 - 16\alpha + 32 \] \[ D = 16\alpha^2 - 80\alpha + 96 \] Setting the discriminant greater than or equal to zero: \[ 16\alpha^2 - 80\alpha + 96 \geq 0 \] Dividing through by 16: \[ \alpha^2 - 5\alpha + 6 \geq 0 \] Factoring the quadratic: \[ (\alpha - 2)(\alpha - 3) \geq 0 \] This inequality holds when: \[ \alpha \leq 2 \quad \text{or} \quad \alpha \geq 3 \] ### Step 3: Condition for roots to be less than \(\frac{1}{2}\) For both roots to be less than \(\frac{1}{2}\), we need the following conditions: 1. The vertex of the parabola, given by \(x = -\frac{b}{2a}\), must be less than \(\frac{1}{2}\). 2. The value of the quadratic at \(x = \frac{1}{2}\) must be positive. Calculating the vertex: \[ x = -\frac{-4\alpha + 8}{2 \cdot 4} = \frac{4\alpha - 8}{8} = \frac{\alpha - 2}{2} \] Setting this less than \(\frac{1}{2}\): \[ \frac{\alpha - 2}{2} < \frac{1}{2} \] Multiplying through by 2: \[ \alpha - 2 < 1 \implies \alpha < 3 \] ### Step 4: Value of the quadratic at \(x = \frac{1}{2}\) 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 0: \[ 3 - \alpha > 0 \implies \alpha < 3 \] ### Step 5: Combine conditions From Step 2, we have \(\alpha \leq 2\) or \(\alpha \geq 3\). From Steps 3 and 4, we have \(\alpha < 3\). The only overlapping condition that satisfies all inequalities is: \[ \alpha \leq 2 \] ### Final Answer Thus, the values of \(\alpha\) for which both roots of the quadratic equation are smaller 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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