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Find all zeros (real and complex) of the polynomial. (Enter your answers as a comma-separated list. Enter all answers using the appropriate multiplicities \[ P(x)=x^{4}-2 x^{3}-7 x^{2}-2 x-8 \] \( x=\square \)

Ask by Young Barrett. in the United States
Mar 11,2025

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Tutor-Verified Answer

Answer

The zeros of the polynomial are \(x = -2\) and \(x = 4\).

Solution

Solve the equation \( x^{4}-2x^{3}-7x^{2}-2x-8=0 \). Solve the equation by following steps: - step0: Solve for \(x\): \(x^{4}-2x^{3}-7x^{2}-2x-8=0\) - step1: Factor the expression: \(\left(x-4\right)\left(x+2\right)\left(x^{2}+1\right)=0\) - step2: Separate into possible cases: \(\begin{align}&x-4=0\\&x+2=0\\&x^{2}+1=0\end{align}\) - step3: Solve the equation: \(\begin{align}&x=4\\&x=-2\\&x \notin \mathbb{R}\end{align}\) - step4: Find the union: \(\begin{align}&x=4\\&x=-2\end{align}\) - step5: Rewrite: \(x_{1}=-2,x_{2}=4\) The zeros of the polynomial \(P(x) = x^{4} - 2x^{3} - 7x^{2} - 2x - 8\) are \(x = -2\) and \(x = 4\).

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Beyond the Answer

To find the zeros of the polynomial \( P(x) = x^{4} - 2x^{3} - 7x^{2} - 2x - 8 \), we can apply the Rational Root Theorem first. Testing possible rational roots (factors of -8), we find \( x = 2 \) is a root. We then perform synthetic division to simplify \( P(x) \) into a cubic polynomial: \[ P(x) = (x - 2)(x^{3} + 2x^{2} - 3x - 4). \] Next, we can further factor \( x^{3} + 2x^{2} - 3x - 4 \). Testing \( x = -2 \) shows it is also a root. Again, perform synthetic division: \[ x^{3} + 2x^{2} - 3x - 4 = (x + 2)(x^{2} - 4). \] The quadratic \( x^{2} - 4 \) can be factored as \( (x - 2)(x + 2) \). Thus, we have: \[ P(x) = (x - 2)^2 (x + 2)^2. \] The complete list of zeros is: \[ x = 2 \text{ (multiplicity 2)}, -2 \text{ (multiplicity 2)}. \] So, the zeros in a comma-separated list are: \( 2, 2, -2, -2 \).

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