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Find all rational zeros of the polynomial, and write the polynomial in factored form. $$ P(x)=8 x^{3}+10 x^{2}-x-3 $$

Short Answer

Expert verified
The rational zeros are \(x = \frac{1}{2}\). In factored form, \(P(x) = (x - \frac{1}{2})(4x + 2)(2x + 3)\).

Step by step solution

01

Apply the Rational Root Theorem

The Rational Root Theorem states that any rational root, in its lowest terms \(\frac{p}{q}\), will have \(p\) as a factor of the constant term and \(q\) as a factor of the leading coefficient. The constant term of \(P(x)\) is \(3\), and its factors are \(±1, ±3\). The leading coefficient is \(8\), and its factors are \(±1, ±2, ±4, ±8\). So, the possible rational zeros are \(\pm 1, \pm \frac{1}{2}, \pm \frac{1}{4}, \pm \frac{1}{8}, \pm 3, \pm \frac{3}{2}, \pm \frac{3}{4}, \pm \frac{3}{8}\).
02

Test possible rational zeros using synthetic division

Test each of these values using synthetic division to see if they are actual zeros. Start with rational numbers by testing \(x = 1\). Synthetic division shows it is not a zero. Continue testing with other possibilities until finding that \(x = \frac{1}{2}\) is a zero.
03

Perform synthetic division for \(x=\frac{1}{2}\)

Perform synthetic division with \(x = \frac{1}{2}\): 1. Write coefficients: 8, 10, -1, -3. 2. Bring down the 8. 3. Multiply \(8\) by \(\frac{1}{2}\) and add to 10 -> new coefficient: 14. 4. Multiply \(14\) by \(\frac{1}{2}\) and add to -1 -> new coefficient: 6. 5. Multiply \(6\) by \(\frac{1}{2}\) and add to -3 -> remainder: 0.New polynomial is \(8x^2 + 14x + 6\).
04

Factor the polynomial \(8x^2 + 14x + 6\)

The quadratic \(8x^2 + 14x + 6\) can be factored using the quadratic formula or by factoring by grouping. The factors are \((4x + 2)(2x + 3)\).
05

Write the polynomial in factored form

Combine the factor from Step 3, \(x - \frac{1}{2}\), with the factors from the quadratic:\[ P(x) = 8(x - \frac{1}{2})(4x + 2)(2x + 3) \]Simplify the polynomial to:\[ P(x) = (x - \frac{1}{2})(4x + 2)(2x + 3) \]

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Key Concepts

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

Polynomial Factoring
Factoring a polynomial means breaking it down into simpler polynomials that, when multiplied together, give the original polynomial. This is an essential exercise in algebra, enabling us to solve polynomials more effectively. To factor a polynomial like \( P(x) = 8x^3 + 10x^2 - x - 3 \), we first use the Rational Root Theorem to identify potential rational roots.

Once a rational root is found using synthetic division, the polynomial is rewritten using that factor, and we continue factoring each remaining polynomial until it cannot be simplified further. By factoring polynomials systematically, you can easily identify all possible solutions to polynomial equations.
Synthetic Division
Synthetic division is a shortcut method for dividing a polynomial by a binomial of the form \( x - c \). It simplifies calculations and can quickly determine whether a certain value is a root of the polynomial. Let’s consider \( P(x) = 8x^3 + 10x^2 - x - 3 \). We use trial and error with synthetic division to find values of \( x \) that make the polynomial equal zero.

In this exercise, after testing several possibilities, it's found that \( x = \frac{1}{2} \) is indeed a zero of the polynomial. Performing synthetic division confirmed this, showing a remainder of zero and leaving behind another polynomial \( 8x^2 + 14x + 6 \). This step is crucial as it allows us to continuously break down the polynomial until it reaches a form that is easier to factor completely.
Factored Form
The factored form of a polynomial is a representation where the polynomial is expressed as a product of its factors. Once a polynomial like \( 8x^3 + 10x^2 - x - 3 \) is broken down, its factored form provides a clear view of its roots. In our solution, after identifying \( x = \frac{1}{2} \) as a root using synthetic division, and factoring the resulting polynomial \( 8x^2 + 14x + 6 \), we further reduce \( P(x) \) to its factored form.

The polynomial was ultimately presented as \( (x - \frac{1}{2})(4x + 2)(2x + 3) \). Expressing polynomials in factored form allows for a more straightforward identification of zeros and simplifies solving polynomial equations, enhancing understanding and ease of further algebraic manipulations.
Quadratic Formula
The quadratic formula is a powerful tool for finding the roots of a quadratic equation. It is applicable when a quadratic expression cannot be factored easily using simple methods. The formula is given by:\[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \]

In the solution of \( 8x^2 + 14x + 6 \) within our polynomial, using the quadratic formula is an alternative to factoring. Although this quadratic can be factored directly into \( (4x + 2)(2x + 3) \), it’s useful to understand how the quadratic formula can achieve the same result. This formula is valuable for complicated quadratics where factors aren’t easily guessed, providing an exact, algebraic solution to finding polynomial roots.

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Most popular questions from this chapter

Find the intercepts and asymptotes, and then sketch a graph of the rational function and state the domain and range. Use a graphing device to confirm your answer. $$ t(x)=\frac{x^{3}-x^{2}}{x^{3}-3 x-2} $$

Find all the real zeros of the polynomial. Use the quadratic formula if necessary, as in Example \(3(\mathrm{a}) .\) $$ P(x)=x^{4}+2 x^{3}-2 x^{2}-3 x+2 $$

Transformations of \(y=1 / x^{2}\) In Example 2 we saw that some simple rational functions can be graphed by shifting, stretching, or reflecting the graph of \(y=1 / x\) . In this exercise we consider rational functions that can be graphed by transforming the graph of \(y=1 / x^{2},\) shown on the following page. (a) Graph the function $$ r(x)=\frac{1}{(x-2)^{2}} $$ by transforming the graph of \(y=1 / x^{2}\) . (b) Use long division and factoring to show that the function $$ s(x)=\frac{2 x^{2}+4 x+5}{x^{2}+2 x+1} $$ can be written as $$ s(x)=2+\frac{3}{(x+1)^{2}} $$ Then graph \(s\) by transforming the graph of \(y=1 / x^{2} .\) (c) One of the following functions can be graphed by trans- forming the graph of \(y=1 / x^{2} ;\) the other cannot. Use transformations to graph the one that can be, and explain why this method doesn't work for the other one. $$ p(x)=\frac{2-3 x^{2}}{x^{2}-4 x+4} \quad q(x)=\frac{12 x-3 x^{2}}{x^{2}-4 x+4} $$

Find the slant asymptote, the vertical asymptotes, and sketch a graph of the function. $$ r(x)=\frac{2 x^{3}+2 x}{x^{2}-1} $$

There are two square roots of \(1,\) namely, 1 and \(-1 .\) These are the solutions of \(x^{2}=1 .\) The fourth roots of 1 are the solutions of the equation \(x^{4}=1\) or \(x^{4}-1=0 .\) How many fourth roots of 1 are there? Find them. The cube roots of 1 are the solutions of the equation \(x^{3}=1\) or \(x^{3}-1=0\) . How many cube roots of 1 are there? Find them. How would you find the sixth roots of 1\(?\) How many are there? Make a conjecture about the number of \(n\) th roots of \(1 .\)

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