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Let alpha ne 1 be a real root of the equ...

Let `alpha ne 1` be a real root of the equation `x^(3) - ax^(2) + ax - 1 = 0,` where a `ne` - 1 is a real number, then a root of this equation, among the following , is :

A

`alpha^2`

B

`-1/(alpha^2)`

C

`1/alpha`

D

`(1)/(alpha^2)`

Text Solution

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The correct Answer is:
To solve the problem, we need to find another root of the equation \( x^3 - ax^2 + ax - 1 = 0 \) given that \( \alpha \) is a root and \( \alpha \neq 1 \). ### Step-by-step Solution: 1. **Substituting the Known Root**: Since \( \alpha \) is a root of the equation, we can substitute \( x = \alpha \) into the equation: \[ \alpha^3 - a\alpha^2 + a\alpha - 1 = 0 \] 2. **Rearranging the Equation**: Rearranging the equation gives us: \[ \alpha^3 = a\alpha^2 - a\alpha + 1 \] 3. **Finding Another Root**: We will check if \( \frac{1}{\alpha} \) is another root of the equation. We substitute \( x = \frac{1}{\alpha} \) into the original equation: \[ \left(\frac{1}{\alpha}\right)^3 - a\left(\frac{1}{\alpha}\right)^2 + a\left(\frac{1}{\alpha}\right) - 1 = 0 \] 4. **Simplifying the Expression**: This simplifies to: \[ \frac{1}{\alpha^3} - \frac{a}{\alpha^2} + \frac{a}{\alpha} - 1 = 0 \] Multiplying through by \( \alpha^3 \) to eliminate the denominators gives: \[ 1 - a\alpha + a\alpha^2 - \alpha^3 = 0 \] 5. **Substituting for \( \alpha^3 \)**: From step 2, we know \( \alpha^3 = a\alpha^2 - a\alpha + 1 \). Substituting this into our equation gives: \[ 1 - a\alpha + a\alpha^2 - (a\alpha^2 - a\alpha + 1) = 0 \] 6. **Simplifying Further**: This simplifies to: \[ 1 - a\alpha + a\alpha^2 - a\alpha^2 + a\alpha - 1 = 0 \] Which simplifies to: \[ 0 = 0 \] This confirms that \( \frac{1}{\alpha} \) satisfies the equation. 7. **Conclusion**: Therefore, \( \frac{1}{\alpha} \) is indeed another root of the equation. ### Final Answer: The root of the equation, among the options given, is \( \frac{1}{\alpha} \).
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