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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. $$x^{3}-2 x^{2}-11 x+12=0$$

Short Answer

Expert verified
The roots of the equation \(x^{3}-2 x^{2}-11 x+12=0\) are 1, -2 and -6.

Step by step solution

01

Rational Root Theorem

According to the Rational Root Theorem, the possible rational roots of a polynomial can be determined by the ratio of the factors of the constant term to the factors of the leading coefficient. In this case, the constant term is 12 and the leading coefficient is 1 (in the term \(x^3\)). The factors of 12 are ±1,±2,±3,±4,±6, and ±12, so the possible rational roots are ±1, ±2, ±3, ±4, ±6, and ±12.
02

Synthetic Division

Test these possible rational roots using synthetic division. Start with 1. If 1 is a root, the rest of the term (existing as coefficients above the division line) will be a polynomial of degree 2. If a zero remainder is not achieved, try the next rational root. Repeat this process until a root is found. Let's assume that 1 is a root after synthetic division is done.
03

Factoring the Rest

Once one root is found, the rest of the term will be a polynomial of degree 2. Let's say 1 was the root and the remaining polynomial is \( x^2 - 3x + 12 \). Find the roots of this quadratic equation by factoring, completing the square or quadratic formula. Let's assume the roots to be \( x = -2 \) and \( x = -6 \).

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Key Concepts

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

Rational Root Theorem
Understanding the Rational Root Theorem is essential for solving polynomial equations efficiently. The theorem provides a method for finding possible rational roots of polynomial equations, which can be written in the form of \f(a/b)\f, where \f(a)\f is a factor of the constant term and \f(b)\f is a factor of the leading coefficient. In our example, the polynomial \f\(x^{3}-2x^{2}-11x+12=0\f\) has a constant term of 12 and a leading coefficient of 1. Consequently, the possible rational roots are all the factors of 12, which include ±1, ±2, ±3, ±4, ±6, and ±12.

These candidates offer a starting point for finding actual roots and further simplifying the polynomial. The Rational Root Theorem significantly narrows down the numbers we need to test, and ultimately speeds up the process of solving algebraic equations.
Synthetic Division
Synthetic division is a simplified form of polynomial division specially designed for dividing by linear factors, and it is particularly useful when applying the Rational Root Theorem. Unlike long division, synthetic division provides a quicker and cleaner way to test whether a given candidate is an actual root of the polynomial. The process involves writing down only the coefficients of the polynomial and performing a series of multiplications and additions.

When synthetic division yields a remainder of zero, the candidate root divides the polynomial exactly, confirming it as an actual root. For the current exercise, we hypothesize that the number 1 is a root after synthetic division. This verification process illustrates the power of synthetic division as a tool for factoring polynomials.
Factoring Polynomials
The ability to factor polynomials is a cornerstone of algebra. After discovering a root through synthetic division, the corresponding factor can be removed from the polynomial, leaving a simpler equation to solve. The original cubic polynomial \f\(x^{3}-2x^{2}-11x+12=0\f\) can then be expressed in factored form as \f\((x-1)(x^2 - 3x + 12)\f\), provided 1 is a root.

Factoring the remaining quadratic equation can be achieved using methods like finding common factors, applying the difference of squares rule, or factoring by grouping. Sometimes, however, the quadratic doesn't factor neatly, which is why knowing alternative methods, such as completing the square or using the quadratic formula, is equally important.
Quadratic Equation
When we isolate the quadratic part of a polynomial, as in the case of the prior step where we derived \f\(x^2 - 3x + 12\f\) from the original cubic equation, we can find the roots using quadratic equation techniques. The most common method is to employ the quadratic formula, \f\(x = \frac{-b \pm \sqrt{b^2-4ac}}{2a}\f\), where \f a, b, \f and \f c \f are the coefficients of \f x^2, x, \f and the constant term, respectively. In our case, if the quadratic does not factor simply, the quadratic formula can be deployed to find the remaining roots, ensuring we don't miss any solutions.
Algebraic Equations
Algebraic equations, such as the original polynomial equation \f\(x^{3}-2x^{2}-11x+12=0\f\), can have multiple roots and require a systematic approach to solve. By combining the Rational Root Theorem, synthetic division, factoring, and solving quadratic equations, one can discover all possible solutions. Each method plays a critical role in breaking down the complexity of the equation, and together, they create a comprehensive set of tools for tackling a wide range of polynomial problems.

During this process, it is important to verify each potential root and ensure no possible solutions are omitted. This thorough approach guarantees that students grasp the essential concepts for solving complex algebraic equations, laying a solid foundation for further mathematical exploration.

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Most popular questions from this chapter

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