To factor the polynomial \( 2x^3 + x^2 - 8x - 4 \) completely, we can use grouping.
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First, we group the terms: \[ (2x^3 + x^2) + (-8x - 4) \]
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Now factor out the common factors in each group: \[ x^2(2x + 1) - 4(2x + 1) \]
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We see that \( (2x + 1) \) is a common factor: \[ (2x + 1)(x^2 - 4) \]
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The expression \( x^2 - 4 \) is a difference of squares, which can be factored further: \[ x^2 - 4 = (x - 2)(x + 2) \]
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Combining all parts, the complete factorization is: \[ (2x + 1)(x - 2)(x + 2) \]
Thus, the complete factorization of the polynomial \( 2x^3 + x^2 - 8x - 4 \) is: \[ \boxed{(2x + 1)(x - 2)(x + 2)} \]