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If x^(2) + px + q = 0 is the quadratic e...

If `x^(2) + px + q = 0` is the quadratic equation whose roots are a-2 and b-2 where a and b are the roots of `x^(2)-3x + 1 = 0` then

A

p = 1, q = 5

B

p = 1, q = -5

C

p = 1, q = 2

D

p = 1, q = -1

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to find the values of \( p \) and \( q \) in the quadratic equation \( x^2 + px + q = 0 \), where the roots are \( a - 2 \) and \( b - 2 \). Here, \( a \) and \( b \) are the roots of the equation \( x^2 - 3x + 1 = 0 \). ### Step 1: Find the roots \( a \) and \( b \) of the equation \( x^2 - 3x + 1 = 0 \). Using the quadratic formula: \[ a, b = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \] For our equation, \( a = 1 \), \( b = -3 \), and \( c = 1 \). Calculating the discriminant: \[ b^2 - 4ac = (-3)^2 - 4 \cdot 1 \cdot 1 = 9 - 4 = 5 \] Now substituting into the quadratic formula: \[ a, b = \frac{3 \pm \sqrt{5}}{2} \] ### Step 2: Calculate the roots \( a \) and \( b \). Thus, the roots are: \[ a = \frac{3 + \sqrt{5}}{2}, \quad b = \frac{3 - \sqrt{5}}{2} \] ### Step 3: Find the new roots \( a - 2 \) and \( b - 2 \). Calculating \( a - 2 \): \[ a - 2 = \frac{3 + \sqrt{5}}{2} - 2 = \frac{3 + \sqrt{5} - 4}{2} = \frac{\sqrt{5} - 1}{2} \] Calculating \( b - 2 \): \[ b - 2 = \frac{3 - \sqrt{5}}{2} - 2 = \frac{3 - \sqrt{5} - 4}{2} = \frac{-\sqrt{5} - 1}{2} \] ### Step 4: Use the new roots to find \( p \) and \( q \). The sum of the roots \( (a - 2) + (b - 2) \): \[ \left( \frac{\sqrt{5} - 1}{2} \right) + \left( \frac{-\sqrt{5} - 1}{2} \right) = \frac{\sqrt{5} - 1 - \sqrt{5} - 1}{2} = \frac{-2}{2} = -1 \] Thus, \( p = -\text{(sum of roots)} = -(-1) = 1 \). The product of the roots \( (a - 2)(b - 2) \): \[ \left( \frac{\sqrt{5} - 1}{2} \right) \left( \frac{-\sqrt{5} - 1}{2} \right) = \frac{(\sqrt{5} - 1)(-\sqrt{5} - 1)}{4} \] Expanding this: \[ = \frac{-5 - \sqrt{5} + \sqrt{5} + 1}{4} = \frac{-4}{4} = -1 \] Thus, \( q = \text{(product of roots)} = -1 \). ### Final Answer: The values of \( p \) and \( q \) are: \[ p = 1, \quad q = -1 \] ---
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