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p(x) be a polynomial of degree at most ...

p(x) be a polynomial of degree at most 5 which leaves remainder - 1 and 1 upon division by `(x-1)^3` and `(x+1)^3`respectively, the number of real roots of `P(x) = 0` is

A

`-(5)/(3)`

B

`-(10)/(3)`

C

`2`

D

`-5`

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The correct Answer is:
To solve the problem, we need to find the number of real roots of the polynomial \( P(x) \) given the conditions on its remainders when divided by \( (x-1)^3 \) and \( (x+1)^3 \). ### Step-by-Step Solution: 1. **Understanding the Polynomial**: Since \( P(x) \) is a polynomial of degree at most 5, we can express it as: \[ P(x) = ax^5 + bx^3 + cx + d \] Here, we note that \( P(x) \) is an odd function due to the nature of the remainders. 2. **Using the Remainder Conditions**: - From the condition \( P(1) = -1 \): \[ a(1)^5 + b(1)^3 + c(1) + d = -1 \implies a + b + c + d = -1 \quad \text{(Equation 1)} \] - From the condition \( P(-1) = 1 \): \[ a(-1)^5 + b(-1)^3 + c(-1) + d = 1 \implies -a - b - c + d = 1 \quad \text{(Equation 2)} \] 3. **Setting Up the System of Equations**: We now have two equations: - \( a + b + c + d = -1 \) (Equation 1) - \( -a - b - c + d = 1 \) (Equation 2) 4. **Solving the System**: We can add Equation 1 and Equation 2: \[ (a + b + c + d) + (-a - b - c + d) = -1 + 1 \] This simplifies to: \[ 2d = 0 \implies d = 0 \] Substituting \( d = 0 \) back into Equation 1: \[ a + b + c = -1 \quad \text{(Equation 3)} \] 5. **Finding the Derivatives**: We differentiate \( P(x) \): \[ P'(x) = 5ax^4 + 3bx^2 + c \] We also need the second derivative: \[ P''(x) = 20ax^3 + 6bx \] 6. **Analyzing the Roots**: Since \( P(x) \) is an odd function, it will have symmetry about the origin. This means if \( P(x) \) has a root at \( x = r \), it will also have a root at \( x = -r \). 7. **Finding the Critical Points**: We need to find the critical points by solving \( P'(x) = 0 \): \[ 5ax^4 + 3bx^2 + c = 0 \] This is a quadratic in \( x^2 \). The number of real roots of \( P'(x) = 0 \) will determine the number of turning points. 8. **Determining the Number of Roots**: Since \( P(x) \) is of degree 5, it can have at most 5 real roots. Given that \( P(x) \) is an odd function and we have established that it has one real root at \( x = 0 \), we need to check the behavior of \( P(x) \) around this point. 9. **Conclusion**: Since \( P(x) \) is a continuous function and changes sign around \( x = 0 \), and given that it is monotonically decreasing (as derived from the negative value of \( P'(0) \)), we conclude that \( P(x) = 0 \) has exactly **one real root**. ### Final Answer: The number of real roots of \( P(x) = 0 \) is **1**.

To solve the problem, we need to find the number of real roots of the polynomial \( P(x) \) given the conditions on its remainders when divided by \( (x-1)^3 \) and \( (x+1)^3 \). ### Step-by-Step Solution: 1. **Understanding the Polynomial**: Since \( P(x) \) is a polynomial of degree at most 5, we can express it as: \[ P(x) = ax^5 + bx^3 + cx + d ...
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