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Ch. 3 - Polynomial and Rational Functions
Lial - College Algebra 13th Edition
Lial13th EditionCollege AlgebraISBN: 9780136881063Not the one you use?Change textbook
Chapter 4, Problem 95

Find all complex zeros of each polynomial function. Give exact values. List multiple zeros as necessary.* ƒ(x)=x4+2x3-3x2+24x-180

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1
Start by writing down the polynomial function: \(f(x) = x^4 + 2x^3 - 3x^2 + 24x - 180\).
Look for possible rational zeros using the Rational Root Theorem. The possible rational zeros are factors of the constant term (\(-180\)) divided by factors of the leading coefficient (which is 1). So, possible rational zeros are \(\pm 1, \pm 2, \pm 3, \pm 5, \pm 6, \pm 9, \pm 10, \pm 15, \pm 18, \pm 30, \pm 45, \pm 60, \pm 90, \pm 180\).
Test these possible rational zeros by substituting them into the polynomial or by using synthetic division to find which values make the polynomial equal to zero. Each successful root will help factor the polynomial.
Once a root \(r\) is found, factor out \((x - r)\) from the polynomial using polynomial division or synthetic division to reduce the polynomial to a cubic or quadratic.
Repeat the process of finding zeros for the reduced polynomial until it is factored completely into linear and/or quadratic factors. Then solve the quadratic factors using the quadratic formula if necessary to find all complex zeros.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Complex Zeros of Polynomial Functions

Complex zeros are the values of x, including real and non-real complex numbers, that make the polynomial equal to zero. According to the Fundamental Theorem of Algebra, a polynomial of degree n has exactly n complex zeros, counting multiplicities. Finding these zeros involves solving the polynomial equation ƒ(x) = 0.
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Polynomial Division and Factoring

Factoring polynomials or using polynomial division (such as synthetic or long division) helps break down higher-degree polynomials into simpler factors. This process is essential to identify zeros by reducing the polynomial to linear or quadratic factors, which can then be solved more easily.
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Quadratic Formula and Solving Quadratics

When a polynomial is factored into quadratic expressions that cannot be factored further, the quadratic formula is used to find the roots. The formula x = (-b ± √(b² - 4ac)) / 2a provides exact solutions, including complex roots when the discriminant is negative.
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Related Practice
Textbook Question

The following exercises are geometric in nature and lead to polynomial models. Solve each problem. A standard piece of notebook paper measuring 8.5 in. by 11 in. is to be made into a box with an open top by cutting equal-size squares from each cor-ner and folding up the sides. Let x represent the length of a side of each such square in inches. Use the table feature of a graphing calculator to do the following. Round to the nearest hundredth.

a. Find the maximum volume of the box.

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Textbook Question

Use the technique described in Exercises 87–90 to solve each inequality. Write the solution set in interval notation. -x2 + 2x + 6 > 0

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Textbook Question

The following exercises are geometric in nature and lead to polynomial models. Solve each problem. A standard piece of notebook paper measuring 8.5 in. by 11 in. is to be made into a box with an open top by cutting equal-size squares from each corner and folding up the sides. Let x represent the length of a side of each such square in inches. Use the table feature of a graphing calculator to do the following. Round to the nearest hundredth.

b. Determine when the volume of the box will be greater than 40 in.3.

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Textbook Question

Determine the different possibilities for the numbers of positive, negative, and nonreal complex zeros of each function. ƒ(x)=2x5+10x46x3+8x2x+1ƒ(x)=-2x^5+10x^4-6x^3+8x^2-x+1

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Textbook Question

Use the technique described in Exercises 87–90 to solve each inequality. Write the solution set in interval notation. 3x2 + x ≥ 4

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Textbook Question

Use the technique described in Exercises 87–90 to solve each inequality. Write the solution set in interval notation. -x2 + 4x + 1 ≥ 0

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