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If |(alpha^(2n),alpha^(2n+2),alpha^(2n+4...

If `|(alpha^(2n),alpha^(2n+2),alpha^(2n+4)),(beta^(2n),beta^(2n+2),beta^(2n+4)),(gamma^(2n),gamma^(2n+2),gamma^(2n+4))|=((1)/(beta^(2))-(1)/(alpha^(2)))((1)/(gamma^(2))-(1)/(beta^(2)))((1)/(alpha^(2))-(1)/(gamma^(2)))`
{where `alpha^(2), beta^(2) and gamma^(2)` are al distinct}, then the value of n is equal to

A

4

B

`-4`

C

3

D

`-2`

Text Solution

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The correct Answer is:
To solve the problem, we need to calculate the determinant on the left-hand side and equate it to the expression on the right-hand side. Here’s the step-by-step solution: ### Step 1: Factor out common terms from the determinant We have: \[ \text{Det} = \begin{vmatrix} \alpha^{2n} & \alpha^{2n+2} & \alpha^{2n+4} \\ \beta^{2n} & \beta^{2n+2} & \beta^{2n+4} \\ \gamma^{2n} & \gamma^{2n+2} & \gamma^{2n+4} \end{vmatrix} \] We can factor out \(\alpha^{2n}\), \(\beta^{2n}\), and \(\gamma^{2n}\) from each row respectively: \[ = \alpha^{2n} \beta^{2n} \gamma^{2n} \begin{vmatrix} 1 & \alpha^2 & \alpha^4 \\ 1 & \beta^2 & \beta^4 \\ 1 & \gamma^2 & \gamma^4 \end{vmatrix} \] ### Step 2: Evaluate the determinant The determinant can be evaluated using the formula for a 3x3 determinant: \[ \begin{vmatrix} 1 & x_1 & x_1^2 \\ 1 & x_2 & x_2^2 \\ 1 & x_3 & x_3^2 \end{vmatrix} = (x_1 - x_2)(x_2 - x_3)(x_3 - x_1) \] In our case, \(x_1 = \alpha^2\), \(x_2 = \beta^2\), \(x_3 = \gamma^2\). Thus, \[ \begin{vmatrix} 1 & \alpha^2 & \alpha^4 \\ 1 & \beta^2 & \beta^4 \\ 1 & \gamma^2 & \gamma^4 \end{vmatrix} = (\alpha^2 - \beta^2)(\beta^2 - \gamma^2)(\gamma^2 - \alpha^2) \] ### Step 3: Combine results Now substituting back, we have: \[ \text{Det} = \alpha^{2n} \beta^{2n} \gamma^{2n} \cdot (\alpha^2 - \beta^2)(\beta^2 - \gamma^2)(\gamma^2 - \alpha^2) \] ### Step 4: Evaluate the right-hand side The right-hand side is given by: \[ \left(\frac{1}{\beta^2} - \frac{1}{\alpha^2}\right)\left(\frac{1}{\gamma^2} - \frac{1}{\beta^2}\right)\left(\frac{1}{\alpha^2} - \frac{1}{\gamma^2}\right) \] Taking the LCM for each term: \[ = \frac{\alpha^2 - \beta^2}{\alpha^2 \beta^2} \cdot \frac{\beta^2 - \gamma^2}{\beta^2 \gamma^2} \cdot \frac{\gamma^2 - \alpha^2}{\gamma^2 \alpha^2} \] ### Step 5: Combine and equate Now we can equate both sides: \[ \alpha^{2n} \beta^{2n} \gamma^{2n} \cdot (\alpha^2 - \beta^2)(\beta^2 - \gamma^2)(\gamma^2 - \alpha^2) = \frac{(\alpha^2 - \beta^2)(\beta^2 - \gamma^2)(\gamma^2 - \alpha^2)}{\alpha^2 \beta^2 \gamma^2} \] ### Step 6: Simplify Canceling \((\alpha^2 - \beta^2)(\beta^2 - \gamma^2)(\gamma^2 - \alpha^2)\) from both sides (since they are non-zero): \[ \alpha^{2n} \beta^{2n} \gamma^{2n} = \frac{1}{\alpha^2 \beta^2 \gamma^2} \] ### Step 7: Solve for \(n\) This implies: \[ \alpha^{2n} \beta^{2n} \gamma^{2n} = \alpha^{-2} \beta^{-2} \gamma^{-2} \] Taking logarithm or comparing powers, we get: \[ 2n = -2 \implies n = -1 \] ### Final Answer Thus, the value of \(n\) is: \[ \boxed{-1} \]
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