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If alpha, beta and gamma are the roots o...

If `alpha, beta and gamma` are the roots of the equation `x^(3) + px + q = 0` (with `p != 0 and p != 0 and q != 0`), the value of the determinant
`|(alpha,beta,gamma),(beta,gamma,alpha),(gamma,alpha,beta)|`, is

A

p

B

q

C

`p^(2) - 2q`

D

none of these

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to evaluate the determinant: \[ D = \begin{vmatrix} \alpha & \beta & \gamma \\ \beta & \gamma & \alpha \\ \gamma & \alpha & \beta \end{vmatrix} \] ### Step 1: Write down the determinant We start with the determinant as given: \[ D = \begin{vmatrix} \alpha & \beta & \gamma \\ \beta & \gamma & \alpha \\ \gamma & \alpha & \beta \end{vmatrix} \] ### Step 2: Use properties of determinants We can perform row operations on the determinant. Specifically, we can add all three rows together and replace the first row with this sum: \[ R_1 \rightarrow R_1 + R_2 + R_3 \] This gives us: \[ D = \begin{vmatrix} \alpha + \beta + \gamma & \alpha + \beta + \gamma & \alpha + \beta + \gamma \\ \beta & \gamma & \alpha \\ \gamma & \alpha & \beta \end{vmatrix} \] ### Step 3: Simplify the determinant Now, notice that the first row consists of the same element repeated three times. Therefore, we can factor out \((\alpha + \beta + \gamma)\): \[ D = (\alpha + \beta + \gamma) \begin{vmatrix} 1 & 1 & 1 \\ \beta & \gamma & \alpha \\ \gamma & \alpha & \beta \end{vmatrix} \] ### Step 4: Find the sum of the roots From the given polynomial \(x^3 + px + q = 0\), we know that the sum of the roots \(\alpha + \beta + \gamma\) is given by: \[ \alpha + \beta + \gamma = -\frac{b}{a} = 0 \] since there is no \(x^2\) term in the polynomial. ### Step 5: Substitute the sum into the determinant Substituting \(\alpha + \beta + \gamma = 0\) into our determinant: \[ D = 0 \cdot \begin{vmatrix} 1 & 1 & 1 \\ \beta & \gamma & \alpha \\ \gamma & \alpha & \beta \end{vmatrix} = 0 \] ### Conclusion Thus, the value of the determinant is: \[ \boxed{0} \]

To solve the problem, we need to evaluate the determinant: \[ D = \begin{vmatrix} \alpha & \beta & \gamma \\ \beta & \gamma & \alpha \\ \gamma & \alpha & \beta \end{vmatrix} ...
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Knowledge Check

  • If alpha,beta,gamma are roots of the equation x^(3)+px+q=0 then the value of |{:(alpha,beta,gamma),(beta,gamma,alpha),(gamma,alpha,beta):}| is

    A
    p
    B
    q
    C
    `p^(2)-4q`
    D
    0
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