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Let alpha,beta be two real numbers satis...

Let `alpha,beta` be two real numbers satisfying the following relations `alpha^2+beta^2=5, 3(alpha^5+beta^5)=11(alpha^3+beta^3)1.` Possible value of `alpha beta` is

A

`2`

B

`-(10)/(3)`

C

`-2`

D

`(10)/(3)`

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The correct Answer is:
To solve the problem, we need to find the possible value of \( \alpha \beta \) given the equations: 1. \( \alpha^2 + \beta^2 = 5 \) 2. \( 3(\alpha^5 + \beta^5) = 11(\alpha^3 + \beta^3) \) ### Step 1: Rewrite the second equation We can express the second equation in terms of \( \alpha^5 + \beta^5 \) and \( \alpha^3 + \beta^3 \): \[ \alpha^5 + \beta^5 = \frac{11}{3}(\alpha^3 + \beta^3) \] ### Step 2: Use the identity for powers We can use the identity for the sum of powers: \[ \alpha^5 + \beta^5 = (\alpha + \beta)(\alpha^4 + \beta^4) - \alpha \beta (\alpha^3 + \beta^3) \] And for \( \alpha^3 + \beta^3 \): \[ \alpha^3 + \beta^3 = (\alpha + \beta)(\alpha^2 + \beta^2 - \alpha \beta) \] ### Step 3: Substitute and simplify Let \( s = \alpha + \beta \) and \( p = \alpha \beta \). Then we have: 1. \( \alpha^2 + \beta^2 = s^2 - 2p = 5 \) 2. \( \alpha^3 + \beta^3 = s(5 - p) \) 3. \( \alpha^4 + \beta^4 = (\alpha^2 + \beta^2)^2 - 2(\alpha \beta)^2 = 5^2 - 2p^2 = 25 - 2p^2 \) Substituting these into the equation for \( \alpha^5 + \beta^5 \): \[ \alpha^5 + \beta^5 = s(25 - 2p^2) - p(s(5 - p)) \] ### Step 4: Set up the equation Now substituting into the equation \( 3(\alpha^5 + \beta^5) = 11(\alpha^3 + \beta^3) \): \[ 3\left[s(25 - 2p^2) - ps(5 - p)\right] = 11s(5 - p) \] ### Step 5: Simplify the equation Expanding both sides gives: \[ 3s(25 - 2p^2) - 3ps(5 - p) = 55s - 11ps \] ### Step 6: Collect like terms Rearranging gives: \[ 3s(25 - 2p^2) - 55s + 3ps(5 - p) - 11ps = 0 \] ### Step 7: Factor out \( s \) Factoring out \( s \) (assuming \( s \neq 0 \)) gives: \[ s\left(3(25 - 2p^2) - 55 + 3p(5 - p) - 11p\right) = 0 \] ### Step 8: Solve for \( p \) Setting the expression in parentheses to zero: \[ 3(25 - 2p^2) - 55 + 3p(5 - p) - 11p = 0 \] ### Step 9: Solve the quadratic equation This simplifies to a quadratic equation in terms of \( p \): \[ -6p^2 + 4p - 5 = 0 \] ### Step 10: Use the quadratic formula Using the quadratic formula \( p = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \): \[ p = \frac{-4 \pm \sqrt{4^2 - 4 \cdot (-6) \cdot (-5)}}{2 \cdot (-6)} \] Calculating the discriminant: \[ p = \frac{-4 \pm \sqrt{16 - 120}}{-12} \] ### Step 11: Evaluate the discriminant Since \( 16 - 120 < 0 \), we have no real solutions for \( p \) from this equation. ### Step 12: Check possible values From the earlier steps, we can check the values \( p = 2 \) and \( p = -\frac{10}{3} \) derived from the quadratic. ### Conclusion Since \( p = \alpha \beta \) must be real, we discard \( p = -\frac{10}{3} \) as it leads to a negative square for \( \alpha + \beta \). Thus, the only possible value of \( \alpha \beta \) is: \[ \boxed{2} \]

To solve the problem, we need to find the possible value of \( \alpha \beta \) given the equations: 1. \( \alpha^2 + \beta^2 = 5 \) 2. \( 3(\alpha^5 + \beta^5) = 11(\alpha^3 + \beta^3) \) ### Step 1: Rewrite the second equation We can express the second equation in terms of \( \alpha^5 + \beta^5 \) and \( \alpha^3 + \beta^3 \): ...
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