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Find all rational zeros of the polynomial. (Enter your answers as a comma-separated list. Enter all answers including repetitions.) \[ P(x)=3 x^{3}+17 x^{2}+21 x-9 \] Write the polynomial in factored form. \( P(x)=\square \)

Ask by Henry Ortiz. in the United States
Feb 27,2025

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The rational zeros are –3, –3, and 1/3. The factored form of the polynomial is \( P(x) = (x + 3)^2(3x - 1) \).

Solución

To find the rational zeros, we use the Rational Root Theorem. For the polynomial   P(x) = 3x³ + 17x² + 21x − 9 the possible rational zeros are of the form (factor of -9)/(factor of 3). The factors of -9 are ±1, ±3, and ±9, and the factors of 3 are ±1, ±3. This gives us the possible zeros:   ±1, ±3, ±9, ±1/3. Step 1. Test the possible zeros. Test x = -3:   P(-3) = 3(-3)³ + 17(-3)² + 21(-3) − 9      = 3(–27) + 17(9) – 63 − 9      = –81 + 153 – 63 − 9      = 0. Since P(-3) = 0, x = -3 is a zero. Step 2. Factor the polynomial by dividing by (x + 3). Using synthetic division with x = -3 and the coefficients 3, 17, 21, -9:   • Bring down the 3.   • Multiply: 3 × (–3) = –9.   • Add to 17: 17 + (–9) = 8.   • Multiply: 8 × (–3) = –24.   • Add to 21: 21 + (–24) = –3.   • Multiply: (–3) × (–3) = 9.   • Add to –9: –9 + 9 = 0. The quotient polynomial is 3x² + 8x – 3. Step 3. Factor the quadratic 3x² + 8x – 3. We solve 3x² + 8x – 3 = 0 using the quadratic formula:   x = [–8 ± √(8² – 4·3·(–3))] / (2·3)     = [–8 ± √(64 + 36)] / 6     = [–8 ± √100] / 6     = [–8 ± 10] / 6 This gives us:   x = (2)/6 = 1/3  and  x = (–18)/6 = –3. So, x = –3 appears again (making it a double root) and the other zero is x = 1/3. Step 4. Write the factored form. Since x = –3 is a zero of multiplicity 2 and x = 1/3 is the remaining zero, the factored form of P(x) is:   P(x) = (x + 3)²(3x – 1). Step 5. List all rational zeros (including repetitions). The rational zeros are:   –3, –3, 1/3. Answer: The rational zeros are –3, –3, 1/3, and the factored form is:   P(x) = (x + 3)²(3x – 1).

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To find the rational zeros of the polynomial \( P(x) = 3x^3 + 17x^2 + 21x - 9 \), we can use the Rational Root Theorem, which suggests that any rational solution will be a combination of factors of the constant term (-9) and the leading coefficient (3). The potential rational roots are: \[ \pm 1, \pm 3, \pm 9, \pm \frac{1}{3}, \pm \frac{3}{3}, \pm \frac{9}{3} \] This simplifies to: \[ \pm 1, \pm 3, \pm 9, \pm \frac{1}{3} \] Testing these values, we find that \( x = 1 \) is a root. Using synthetic division with \( x - 1 \), we divide the polynomial by this root: \[ P(x) = (x - 1)(3x^2 + 20x + 9) \] Next, we find the zeros of the quadratic \( 3x^2 + 20x + 9 \) using the quadratic formula: \[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} = \frac{-20 \pm \sqrt{400 - 108}}{6} = \frac{-20 \pm \sqrt{292}}{6} = \frac{-20 \pm 2\sqrt{73}}{6} = \frac{-10 \pm \sqrt{73}}{3} \] Thus, the rational roots are simply \( x = 1 \) with multiplicity, and the additional zeros are irrational. In total: The rational zeros of \( P(x) \): \( 1 \), \( 1 \), \( 1 \) The polynomial in factored form is: \[ P(x) = (x - 1)^3(3x^2 + 20x + 9) \] Now let's provide some engaging knowledge! The discovery of rational roots can feel like a treasure hunt for mathematicians! By using clever techniques like synthetic division, you can simplify complex polynomials into manageable factors. This method transforms what seems daunting into a series of straightforward steps—almost like following a recipe in the kitchen! Once you find those elusive roots, it's time to highlight their importance. Understanding rational roots doesn't just help in solving equations; it also plays a critical role in fields such as engineering and physics, where polynomial equations frequently arise. Whether it's calculating trajectories or modeling dynamic systems, rational roots ensure you have accurate solutions that can lead to innovative designs!

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