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If alpha, beta, gamma are the roots of t...

If `alpha, beta, gamma` are the roots of the equation `x^(3) + x + 1 = 0`, then the value of `alpha^(3) + beta^(3) + gamma^(3)`, is

A

0

B

3

C

-3

D

-1

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The correct Answer is:
To find the value of \( \alpha^3 + \beta^3 + \gamma^3 \) where \( \alpha, \beta, \gamma \) are the roots of the equation \( x^3 + x + 1 = 0 \), we can follow these steps: ### Step 1: Identify the coefficients of the cubic equation The given equation is: \[ x^3 + 0x^2 + x + 1 = 0 \] From this, we can identify: - \( A = 1 \) (coefficient of \( x^3 \)) - \( B = 0 \) (coefficient of \( x^2 \)) - \( C = 1 \) (coefficient of \( x \)) - \( D = 1 \) (constant term) ### Step 2: Use Vieta's formulas to find the sums and products of the roots According to Vieta's formulas: - The sum of the roots \( \alpha + \beta + \gamma = -\frac{B}{A} = -\frac{0}{1} = 0 \) - The sum of the product of the roots taken two at a time \( \alpha\beta + \beta\gamma + \gamma\alpha = \frac{C}{A} = \frac{1}{1} = 1 \) - The product of the roots \( \alpha\beta\gamma = -\frac{D}{A} = -\frac{1}{1} = -1 \) ### Step 3: Use the identity for the sum of cubes There is an important identity that relates the sum of cubes of the roots to the roots themselves: \[ \alpha^3 + \beta^3 + \gamma^3 = 3\alpha\beta\gamma + (\alpha + \beta + \gamma)(\alpha^2 + \beta^2 + \gamma^2 - \alpha\beta - \beta\gamma - \gamma\alpha) \] Since we know that \( \alpha + \beta + \gamma = 0 \), the second term becomes zero: \[ \alpha^3 + \beta^3 + \gamma^3 = 3\alpha\beta\gamma \] ### Step 4: Substitute the product of the roots Now, substituting the value of \( \alpha\beta\gamma \): \[ \alpha^3 + \beta^3 + \gamma^3 = 3(-1) = -3 \] ### Final Answer Thus, the value of \( \alpha^3 + \beta^3 + \gamma^3 \) is: \[ \boxed{-3} \]

To find the value of \( \alpha^3 + \beta^3 + \gamma^3 \) where \( \alpha, \beta, \gamma \) are the roots of the equation \( x^3 + x + 1 = 0 \), we can follow these steps: ### Step 1: Identify the coefficients of the cubic equation The given equation is: \[ x^3 + 0x^2 + x + 1 = 0 \] From this, we can identify: ...
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