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Let g(x) and h(x) be two polynomials wit...

Let g(x) and h(x) be two polynomials with real coefficients. If `p(x) = g(x^(3)) + xh(x^(3))` is divisible by `x^(2) + x + 1`, then

A

g(1) = 0, h(1) = 1

B

g(1) = 1, h(1) = 0

C

g(1) = 0, h(1) = 0

D

g(1) = 1, h(1) = 0

Text Solution

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The correct Answer is:
To solve the problem, we need to analyze the polynomial \( p(x) = g(x^3) + xh(x^3) \) and determine the conditions under which it is divisible by \( x^2 + x + 1 \). ### Step-by-Step Solution: 1. **Identify the Roots of the Divisor**: The polynomial \( x^2 + x + 1 \) has roots which can be found using the quadratic formula: \[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} = \frac{-1 \pm \sqrt{1^2 - 4 \cdot 1 \cdot 1}}{2 \cdot 1} = \frac{-1 \pm \sqrt{-3}}{2} = \frac{-1 \pm i\sqrt{3}}{2} \] Let \( \omega = \frac{-1 + i\sqrt{3}}{2} \) and \( \omega^2 = \frac{-1 - i\sqrt{3}}{2} \). 2. **Evaluate \( p(\omega) \)**: Since \( p(x) \) is divisible by \( x^2 + x + 1 \), we have: \[ p(\omega) = g(\omega^3) + \omega h(\omega^3) = 0 \] We know that \( \omega^3 = 1 \). Therefore: \[ p(\omega) = g(1) + \omega h(1) = 0 \] This gives us our first equation: \[ g(1) + \omega h(1) = 0 \quad \text{(Equation 1)} \] 3. **Evaluate \( p(\omega^2) \)**: Similarly, we evaluate \( p(\omega^2) \): \[ p(\omega^2) = g((\omega^2)^3) + \omega^2 h((\omega^2)^3) = g(1) + \omega^2 h(1) = 0 \] This gives us our second equation: \[ g(1) + \omega^2 h(1) = 0 \quad \text{(Equation 2)} \] 4. **Set Up the System of Equations**: Now we have two equations: - From Equation 1: \( g(1) + \omega h(1) = 0 \) - From Equation 2: \( g(1) + \omega^2 h(1) = 0 \) 5. **Subtract the Equations**: Subtract Equation 2 from Equation 1: \[ (g(1) + \omega h(1)) - (g(1) + \omega^2 h(1)) = 0 \] This simplifies to: \[ \omega h(1) - \omega^2 h(1) = 0 \implies h(1)(\omega - \omega^2) = 0 \] 6. **Analyze the Result**: Since \( \omega \neq \omega^2 \), we conclude that: \[ h(1) = 0 \] 7. **Substituting Back**: Substitute \( h(1) = 0 \) back into either Equation 1 or Equation 2: \[ g(1) + \omega \cdot 0 = 0 \implies g(1) = 0 \] ### Final Result: Thus, we have: \[ g(1) = 0 \quad \text{and} \quad h(1) = 0 \] ### Conclusion: The polynomials \( g(x) \) and \( h(x) \) must satisfy \( g(1) = 0 \) and \( h(1) = 0 \). Therefore, both \( g(1) \) and \( h(1) \) are equal to zero.
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