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If x(1),x(2),x(3),…,x(n) are the roots o...

If `x_(1),x_(2),x_(3),…,x_(n)` are the roots of the equation `x^(n)+ax+b=0`, the value of
`(x_(1)-x_(2))(x_(1)-x_(3))(x_(1)-x_(4))…….(x_(1)-x_(n))` is

A

`nx _(1) +b`

B

` n x _(1)^(n-1) +a`

C

`nx _(1) ^(n-1)`

D

`nx _(1) ^(n-1)`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to find the value of the expression: \[ (x_1 - x_2)(x_1 - x_3)(x_1 - x_4) \ldots (x_1 - x_n) \] where \(x_1, x_2, x_3, \ldots, x_n\) are the roots of the polynomial equation: \[ x^n + ax + b = 0 \] ### Step-by-Step Solution: 1. **Understand the Polynomial Representation**: The polynomial can be expressed in terms of its roots as: \[ x^n + ax + b = (x - x_1)(x - x_2)(x - x_3) \ldots (x - x_n) \] 2. **Divide by \(x - x_1\)**: We can divide both sides of the equation by \(x - x_1\): \[ \frac{x^n + ax + b}{x - x_1} = (x - x_2)(x - x_3) \ldots (x - x_n) \] 3. **Take the Limit as \(x\) Approaches \(x_1\)**: We take the limit as \(x\) approaches \(x_1\): \[ \lim_{x \to x_1} \frac{x^n + ax + b}{x - x_1} = \lim_{x \to x_1} (x - x_2)(x - x_3) \ldots (x - x_n) \] 4. **Differentiate the Numerator and Denominator**: Since both the numerator and denominator approach 0 as \(x\) approaches \(x_1\), we apply L'Hôpital's Rule: - Differentiate the numerator: \[ \frac{d}{dx}(x^n + ax + b) = nx^{n-1} + a \] - The derivative of the denominator is: \[ \frac{d}{dx}(x - x_1) = 1 \] 5. **Evaluate the Limit**: Now we evaluate the limit: \[ \lim_{x \to x_1} \frac{nx^{n-1} + a}{1} = n x_1^{n-1} + a \] 6. **Evaluate the Right Side**: On the right side, we can directly substitute \(x = x_1\): \[ (x_1 - x_2)(x_1 - x_3) \ldots (x_1 - x_n) \] 7. **Final Equation**: Setting both sides equal gives us: \[ n x_1^{n-1} + a = (x_1 - x_2)(x_1 - x_3) \ldots (x_1 - x_n) \] 8. **Conclusion**: Therefore, the value of the expression \((x_1 - x_2)(x_1 - x_3)(x_1 - x_4) \ldots (x_1 - x_n)\) is equal to \(n x_1^{n-1} + a\). ### Final Answer: \[ \text{The value is } n x_1^{n-1} + a \]
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