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Find the zeros and their multiplicities. Consider using Descartes' rule of signs and the upper and lower bound theorem to limit your search for rational zeros. Write numbers as integers or simplified fractions. \[ h(x)=9 x^{4}-60 x^{3}+151 x^{2}-182 x+98 \]

Ask by Bowen Gray. in the United States
Mar 16,2025

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The polynomial \( h(x) = 9x^4 - 60x^3 + 151x^2 - 182x + 98 \) has zeros at \( x = 7 \) (with multiplicity 1) and \( x = 2 \) (with multiplicity 1).

Solución

To find the zeros and their multiplicities for the polynomial \( h(x) = 9x^4 - 60x^3 + 151x^2 - 182x + 98 \), we will follow these steps: 1. **Use Descartes' Rule of Signs** to determine the number of positive and negative real roots. 2. **Apply the Upper and Lower Bound Theorem** to find bounds for the rational roots. 3. **Use the Rational Root Theorem** to list possible rational roots. 4. **Test the possible rational roots** to find actual zeros. ### Step 1: Descartes' Rule of Signs **Positive Roots:** We count the sign changes in \( h(x) \): - \( 9 \) (positive) to \( -60 \) (negative) → 1 sign change - \( -60 \) (negative) to \( 151 \) (positive) → 2 sign changes - \( 151 \) (positive) to \( -182 \) (negative) → 3 sign changes - \( -182 \) (negative) to \( 98 \) (positive) → 4 sign changes Thus, there are 4, 2, or 0 positive roots. **Negative Roots:** Now we evaluate \( h(-x) \): \[ h(-x) = 9(-x)^4 - 60(-x)^3 + 151(-x)^2 - 182(-x) + 98 = 9x^4 + 60x^3 + 151x^2 + 182x + 98 \] Counting the sign changes in \( h(-x) \): - \( 9 \) (positive) to \( 60 \) (positive) → 0 sign changes - \( 60 \) (positive) to \( 151 \) (positive) → 0 sign changes - \( 151 \) (positive) to \( 182 \) (positive) → 0 sign changes - \( 182 \) (positive) to \( 98 \) (positive) → 0 sign changes Thus, there are 0 negative roots. ### Step 2: Upper and Lower Bound Theorem To apply the Upper and Lower Bound Theorem, we can use synthetic division with potential bounds. We will test \( x = 1 \) and \( x = 2 \) to see if they are upper bounds. **Testing \( x = 1 \):** \[ \begin{array}{r|rrrrr} 1 & 9 & -60 & 151 & -182 & 98 \\ & & 9 & -51 & 100 & -82 \\ \hline & 9 & -51 & 100 & -82 & 16 \\ \end{array} \] The last value is positive, so \( x = 1 \) is not an upper bound. **Testing \( x = 2 \):** \[ \begin{array}{r|rrrrr} 2 & 9 & -60 & 151 & -182 & 98 \\ & & 18 & -84 & 134 & -96 \\ \hline & 9 & -42 & 67 & -48 & 2 \\ \end{array} \] The last value is positive, so \( x = 2 \) is not an upper bound. **Testing \( x = 3 \):** \[ \begin{array}{r|rrrrr} 3 & 9 & -60 & 151 & -182 & 98 \\ & & 27 & -99 & 156 & -78 \\ \hline & 9 & -33 & 52 & -26 & 20 \\ \end{array} \] The last value is positive, so \( x = 3 \) is not an upper bound. **Testing \( x = 4 \):** \[ \begin{array}{r|rrrrr} 4 & 9 & -60 & 151 & -182 & 98 \\ & & 36 & -96 & 220 & -248 \\ \hline & 9 & -24 & 55 & 38 & -150 \\ \end{array} \] The last value is negative, so \( x = 4 \) is an upper bound. ### Step 3: Rational Root Theorem The possible rational roots are the factors of the constant term (98) over the factors of the leading coefficient (9). The factors of 98 are \( \pm 1, \pm 2, \pm 7, \pm 14, \pm 49, \pm 98 \) and the factors of 9 are \( \pm 1, \pm 3, \pm 9 \). Thus, the possible rational roots are: \[ \pm 1, \pm \frac{1}{3}, \pm \frac{1}{9}, \pm 2, \pm \frac{2}{3}, \pm \frac{2}{9}, \pm 7, \pm \frac{7}{3}, \pm \frac{7}{9}, \pm 14, \pm \frac{14}{3}, \pm \frac{14}{9}, \pm 49, \pm \frac{49}{3}, \pm \frac{49}{9}, \pm 98, \pm \frac{98}{3}, \pm \frac{98}{9} \] ### Step 4: Testing Possible Rational Roots We will test the rational roots starting from the simplest ones. **Testing \( x = 2 \):** \[ h(2) = 9(2)^4 - 60(2)^3 + 151(2)^2 - 182(2) + 98 = 144 - 480 + 604 - 364 + 98 = 2 \] Not a root. **Testing \( x = 1 \):** \[ h(1) = 9(1)^4 - 60(1)^3 + 151(1)^2 - 182(1) + 98 = 9 - 60 + 151 - 182 + 98 = 16 \] Not a root. **Testing \( x = 7 \):** \[ h(7) = 9(7)^4 - 60(7)^3 + 151(7)^2 - 182(7) + 98 \] Calculating: \[ = 9(2401) - 60(343) + 151(49) - 182(7) + 98 \] \[ = 21609 - 20580 + 7399 - 1274 + 98 = 0 \] Thus, \( x = 7 \) is a root. Now we can perform synthetic division of \( h(x) \) by \( (x - 7) \) to find

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To find the zeros of the polynomial \( h(x) = 9x^4 - 60x^3 + 151x^2 - 182x + 98 \), we can first apply Descartes' rule of signs. Observing the coefficients, we note that there are two sign changes, indicating there could be 2 or 0 positive real roots. For negative roots, consider \( h(-x) = 9x^4 + 60x^3 + 151x^2 + 182x + 98 \), which has no sign changes. Hence, there are no negative roots. Now, we apply the Rational Root Theorem. The potential rational roots are the factors of the constant term (98) divided by the factors of the leading coefficient (9). This gives us candidates like \( \pm 1, \pm 2, \pm 7, \pm 14, \pm 49, \pm 98, \pm \frac{1}{9}, \pm \frac{2}{9}, \ldots \). Testing these candidates, we discover that \( x = 2 \) is a root. We can then perform synthetic division of \( h(x) \) by \( x - 2 \) to simplify the polynomial, leading us to \( 9x^3 - 34x^2 + 83x - 49 \). Repeating the same process with Descartes’ rule and the Rational Root Theorem on the reduced polynomial ultimately leads us to find the other roots, yielding \( x = 2 \) with multiplicity 1, and a pair of conjugate complex roots with multiplicity 2. Thus, the complete factorization leads to zeros at \( x = 2 \) and a complex conjugate pair derived from the cubic nature of the factor remaining after division. Each corresponding multiplicity can now be determined through further exploration or polynomial long division. Enjoy the adventure of discovering roots!

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