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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 imaginary

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To find the values of \( \alpha \) for which the roots of the quadratic equation \( 4x^2 - 4(\alpha - 2)x + (\alpha - 2) = 0 \) are imaginary, we need to analyze the discriminant of the equation. ### Step 1: Identify the coefficients The standard form of a quadratic equation is \( ax^2 + bx + c = 0 \). Here, we can identify: - \( a = 4 \) - \( b = -4(\alpha - 2) \) - \( c = \alpha - 2 \) ### Step 2: Write the discriminant The discriminant \( D \) of a quadratic equation is given by: \[ D = b^2 - 4ac \] Substituting the values of \( a \), \( b \), and \( c \): \[ D = \left(-4(\alpha - 2)\right)^2 - 4 \cdot 4 \cdot (\alpha - 2) \] ### Step 3: Simplify the discriminant Calculating \( D \): \[ D = 16(\alpha - 2)^2 - 16(\alpha - 2) \] Factoring out \( 16 \): \[ D = 16\left((\alpha - 2)^2 - (\alpha - 2)\right) \] Let \( y = \alpha - 2 \): \[ D = 16(y^2 - y) \] ### Step 4: Set the discriminant less than zero For the roots to be imaginary, the discriminant must be less than zero: \[ 16(y^2 - y) < 0 \] This simplifies to: \[ y^2 - y < 0 \] ### Step 5: Factor the inequality Factoring the quadratic: \[ y(y - 1) < 0 \] ### Step 6: Determine the intervals The roots of the equation \( y(y - 1) = 0 \) are \( y = 0 \) and \( y = 1 \). We analyze the sign of the product \( y(y - 1) \) in the intervals: - \( y < 0 \) (both factors negative, product positive) - \( 0 < y < 1 \) (one factor positive and one negative, product negative) - \( y > 1 \) (both factors positive, product positive) Thus, the inequality \( y(y - 1) < 0 \) holds for: \[ 0 < y < 1 \] ### Step 7: Substitute back for \( \alpha \) Recalling that \( y = \alpha - 2 \): \[ 0 < \alpha - 2 < 1 \] Adding 2 to all parts of the inequality: \[ 2 < \alpha < 3 \] ### Conclusion The values of \( \alpha \) for which both roots of the quadratic equation are imaginary are: \[ \alpha \in (2, 3) \]
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FIITJEE-QUADRATIC EQUATION & EXPRESSION -ASSIGNMENT PROBLEMS (SUBJECTIVE) Level - II
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