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If alpha and beta are the roots of the e...

If `alpha` and `beta` are the roots of the equation `2x^(2)+4x-5=0`, then the equation whose roots are `(1)/(2alpha-3) and (1)/(2beta-3)` is

A

`x^(2)+10x-11=0`

B

`11x^(2)+10x+1=0`

C

`x^(2)+10x+11=0`

D

`11x^(2)-10x+1=0`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to find the equation whose roots are given by \( \frac{1}{2\alpha - 3} \) and \( \frac{1}{2\beta - 3} \), where \( \alpha \) and \( \beta \) are the roots of the quadratic equation \( 2x^2 + 4x - 5 = 0 \). ### Step 1: Find the roots \( \alpha \) and \( \beta \) of the equation \( 2x^2 + 4x - 5 = 0 \). Using the quadratic formula: \[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \] where \( a = 2 \), \( b = 4 \), and \( c = -5 \). Calculating the discriminant: \[ b^2 - 4ac = 4^2 - 4 \cdot 2 \cdot (-5) = 16 + 40 = 56 \] Now substituting into the quadratic formula: \[ x = \frac{-4 \pm \sqrt{56}}{2 \cdot 2} = \frac{-4 \pm 2\sqrt{14}}{4} = \frac{-2 \pm \sqrt{14}}{2} \] Thus, the roots are: \[ \alpha = \frac{-2 + \sqrt{14}}{2}, \quad \beta = \frac{-2 - \sqrt{14}}{2} \] ### Step 2: Express the new roots in terms of \( \alpha \) and \( \beta \). The new roots are: \[ y_1 = \frac{1}{2\alpha - 3}, \quad y_2 = \frac{1}{2\beta - 3} \] ### Step 3: Find \( 2\alpha - 3 \) and \( 2\beta - 3 \). Calculating \( 2\alpha \) and \( 2\beta \): \[ 2\alpha = -2 + \sqrt{14}, \quad 2\beta = -2 - \sqrt{14} \] Thus, \[ 2\alpha - 3 = -5 + \sqrt{14}, \quad 2\beta - 3 = -5 - \sqrt{14} \] ### Step 4: Find the new roots \( y_1 \) and \( y_2 \). Calculating \( y_1 \) and \( y_2 \): \[ y_1 = \frac{1}{-5 + \sqrt{14}}, \quad y_2 = \frac{1}{-5 - \sqrt{14}} \] ### Step 5: Find the sum and product of the new roots. Using the formulas for the sum and product of roots: \[ \text{Sum} = y_1 + y_2 = \frac{1}{-5 + \sqrt{14}} + \frac{1}{-5 - \sqrt{14}} = \frac{(-5 - \sqrt{14}) + (-5 + \sqrt{14})}{(-5 + \sqrt{14})(-5 - \sqrt{14})} \] \[ = \frac{-10}{(-5)^2 - (\sqrt{14})^2} = \frac{-10}{25 - 14} = \frac{-10}{11} \] For the product: \[ \text{Product} = y_1 \cdot y_2 = \left(\frac{1}{-5 + \sqrt{14}}\right) \left(\frac{1}{-5 - \sqrt{14}}\right) = \frac{1}{(-5 + \sqrt{14})(-5 - \sqrt{14})} = \frac{1}{25 - 14} = \frac{1}{11} \] ### Step 6: Form the new quadratic equation. Using the sum and product of the roots, we can form the quadratic equation: \[ x^2 - \left(\text{Sum}\right)x + \text{Product} = 0 \] Substituting the values: \[ x^2 + \frac{10}{11}x + \frac{1}{11} = 0 \] Multiplying through by 11 to eliminate the fractions: \[ 11x^2 + 10x + 1 = 0 \] ### Final Answer: The required equation is: \[ \boxed{11x^2 + 10x + 1 = 0} \]
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Knowledge Check

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