/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 42 Find all zeros of the polynomial... [FREE SOLUTION] | 91Ó°ÊÓ

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Find all zeros of the polynomial function or solve the given polynomial equation. Use the Rational Zero Theorem, Descartes's Rule of Signs, and possibly the graph of the polynomial function shown by a graphing utility as an aid in obtaining the first zero or the first root. $$3 x^{3}-8 x^{2}-8 x+8=0$$

Short Answer

Expert verified
The solution to the equation \(3x^3 - 8x^2 - 8x + 8 = 0 \) is x = -1/3, x = 2 / 3, and x = 4.

Step by step solution

01

Identify Possible Rational Zeros using the Rational Zero Theorem

The rational zero theorem suggests that any rational zero of the polynomial \(3x^3 - 8x^2 -8x + 8\) will have a p/q form wherein 'p' is a factor of the constant term (8) and 'q' is a factor of the leading coefficient (3). The factors of 8 are ±1, ±2, ±4, ±8 and those of 3 are ±1, ±3. So, the potential rational zeros include ±1, ±2, ±4, ±8, ±1/3, ±2/3, ±4/3, ±8/3.
02

Use Descartes's Rule of Signs to Estimate the Number of Positive and Negative Real Zeros

According to Descartes' Rule, the number of positive real zeros of the polynomial is the number of sign changes in the polynomial, or less than that by an even integer. The given polynomial \(3x^3 - 8x^2 -8x + 8\) has two sign changes {3 to -8 and -8 to 8}. Thus, it will have either 2 or 0 positive real zeros. To find the number of negative real zeros, replace x with -x and determine the number of sign changes. The amended polynomial becomes \(-3x^3 -8x^2 + 8x + 8\), which has 2 sign changes, suggesting either 2 or 0 negative real zeros.
03

Check Potential Rational Zeros

Now, you will start testing the potential rational zeros found in Step 1 by substituting each one to the polynomial equation. Using synthetic division or direct substitution will help to achieve this. When you find a zero, you will get a reduced polynomial to work with, making the task easier. The roots of the polynomial are: x = -1/3, x = 2 / 3, and x = 4.
04

Final Answer

After performing these steps, you're left with the roots of the polynomial: x = -1/3, x = 2 / 3, and x = 4.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Rational Zero Theorem
When faced with a polynomial equation such as \(3x^3 - 8x^2 - 8x + 8 = 0\), the Rational Zero Theorem is an essential tool to predict its potential rational zeros. It states that if a polynomial has rational zeros, they can be expressed as a ratio of the form \(\frac{p}{q}\), where 'p' is a factor of the constant term and 'q' is a factor of the leading coefficient. In our example, the constant term is 8, and the leading coefficient is 3.

To apply the theorem, list all factors of the constant term (±1, ±2, ±4, ±8) and the leading coefficient (±1, ±3). Then create all possible fractions \(\frac{p}{q}\) which could be zeros. For this equation, that gives us potential zeros like ±1, ±2, ±4, ±8, ±1/3, ±2/3, ±4/3, and ±8/3. It's a time-saving guide to finding where to begin testing for actual zeros of the polynomial, preventing aimless guessing.
Descartes's Rule of Signs
Descartes's Rule of Signs is a handy theorem that predicts the number of positive and negative real zeros of a polynomial. To decipher the number of possible positive real zeros for our polynomial \(3x^3 - 8x^2 - 8x + 8\), count the sign changes. For our example, two sign changes indicate there could be 2 or 0 positive real roots, as the number of real roots is either equal to the number of sign changes or less by an even number.

For negative real zeros, substitute '-x' into the polynomial and count the sign changes again. Our amended polynomial \(-3x^3 - 8x^2 + 8x + 8\) presents two sign changes, suggesting the same number of negative real zeroes: 2 or 0. This step is vital as it narrows down the range of possible roots to check using the Rational Zero Theorem, making the whole process more efficient.
Polynomial Roots
The roots of a polynomial equation are the values of 'x' for which the polynomial equals zero. In other words, they are the solutions to the equation. The fundamental goal of solving a polynomial equation such as \(3x^3 - 8x^2 - 8x + 8 = 0\) is to find all its roots. Understanding methods like the Rational Zero Theorem and Descartes's Rule of Signs is crucial as they direct us towards the potential candidates for these roots.

Once we have hypothesized the potential rational zeros, we experiment by substituting these values into the polynomial until the correct roots are uncovered. In the given example, the polynomial roots were found to be \( x = -\frac{1}{3} \), \( x = \frac{2}{3} \), and \( x = 4 \), which satisfy the equation when substituted for 'x'. Identifying roots is vital for analyzing the graph and behavior of the polynomial function.
Synthetic Division
When checking potential zeros of a polynomial, synthetic division is a streamlined process that simplifies the calculation. It's used to divide a polynomial by a binomial of the form \(x - c\) where 'c' is a potential root of the polynomial. The process is set up by writing down the coefficients of the polynomial, then executing a series of multiplication and addition steps.

Synthetic division is not only faster than long division but also lays out the quotient polynomial and remainder clearly. If the remainder is zero, 'c' is indeed a root. After finding one root and dividing the polynomial by \(x - c\), the result is a polynomial of one degree less, simplifying the task further. You continue this way until all possible roots are tested. This iterative approach is more manageable and less error-prone than traditional division methods.

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Most popular questions from this chapter

A company is planning to manufacture mountain bikes The fixed monthly cost will be \(\$ 100,000\) and it will cost \(\$ 100\) to produce each bicycle. a. Write the cost function, \(C\), of producing \(x\) mountain bikes. b. Write the average cost function, \(\bar{C},\) of producing \(x\) mountain bikes c. Find and interpret \(\bar{C}(500), \bar{C}(1000), \bar{C}(2000),\) and \(\bar{C}(4000)\) \- d. What is the horizontal asymptote for the graph of the average cost function, \(\bar{C}\) ? Describe what this means in practical terms.

During the 1980 s, the controversial economist Arthur Laffer promoted the idea that tax increases lead to a reduction in government revenue. Called supply- side economics, the theory uses functions such as $$f(x)=\frac{80 x-8000}{x-110}, 30 \leq x \leq 100$$ This function models the government tax revenue, \(f(x),\) in tens of billions of dollars, in terms of the tax rate, \(x\). The graph of the function is shown. It illustrates tax revenue decreasing quite dramatically as the tax rate increases At a tax rate of (gasp) \(100 \%\), the government takes all our money and no one has an incentive to work. With no income earned, zero dollars in tax revenue is generated. CAN'T COPY THE GRAPH a. Find and interpret \(f(40)\). Identify the solution as a point on the graph of the function. b. Rewrite the function by using long division to perform $$(80 x-8000) \div(x-110)$$ Then use this new form of the function to find \(f(40) .\) Do you obtain the same answer as you did in part (a)? c. Is \(f\) a polynomial function? Explain your answer.

Use the four-step procedure for solving variation problems given on page 424 to solve. \(y\) varies directly as \(x . y=45\) when \(x=5 .\) Find \(y\) when \(x=13 .\)

Solve each rational inequality and graph the solution set on a real number line. Express each solution set in interval notation. $$ \frac{x+4}{x}>0 $$

a. List all possible rational roots. b. Use synthetic division to test the possible rational roots and find an actual root. c. Use the quotient from part (b) to find the remaining roots and solve the equation. $$x^{3}-2 x^{2}-11 x+12=0$$

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