The rule for rewriting an absolute value equation without absolute value bars can be extended to equations with two sets of absolute value bars: If u and v represent algebraic expressions, then |u| = |v| is equivalent to u = v or u = - v. Use this to solve the equations in Exercises 77–84.
Table of contents
- 0. Review of Algebra4h 18m
- 1. Equations & Inequalities3h 18m
- 2. Graphs of Equations1h 43m
- 3. Functions2h 17m
- 4. Polynomial Functions1h 44m
- 5. Rational Functions1h 23m
- 6. Exponential & Logarithmic Functions2h 28m
- 7. Systems of Equations & Matrices4h 5m
- 8. Conic Sections2h 23m
- 9. Sequences, Series, & Induction1h 22m
- 10. Combinatorics & Probability1h 45m
1. Equations & Inequalities
The Quadratic Formula
Problem 89
Textbook Question
Use the method described in Exercises 83–86, if applicable, and properties of absolute value to solve each equation or inequality. (Hint: Exercises 99 and 100 can be solved by inspection.) | 3x2 - 14x | = 5
Verified step by step guidance1
Recognize that the equation involves an absolute value: \(|3x^2 - 14x| = 5\). The definition of absolute value tells us that \(|A| = B\) means \(A = B\) or \(A = -B\) when \(B \geq 0\).
Set up two separate equations based on the absolute value property:
\$3x^2 - 14x = 5\(
and
\)3x^2 - 14x = -5$.
Solve each quadratic equation separately. For the first equation \$3x^2 - 14x - 5 = 0\(, use the quadratic formula:
\)x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}\(,
where \)a=3\(, \)b=-14\(, and \)c=-5$.
Similarly, solve the second quadratic equation \$3x^2 - 14x + 5 = 0\( using the quadratic formula with \)a=3\(, \)b=-14\(, and \)c=5$.
After finding the solutions from both quadratics, check each solution by substituting back into the original absolute value equation to ensure they satisfy \(|3x^2 - 14x| = 5\).
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Absolute Value Equations
An absolute value equation involves expressions within absolute value bars, which represent the distance from zero on the number line. To solve |A| = B, where B ≥ 0, we set A = B and A = -B, creating two separate equations to solve. Understanding this principle is essential for breaking down the given equation.
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Quadratic Equations
Quadratic equations are polynomial equations of degree two, typically in the form ax² + bx + c = 0. Solving them involves factoring, completing the square, or using the quadratic formula. Since the expression inside the absolute value is quadratic, solving the resulting equations requires knowledge of these methods.
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Properties of Absolute Value Inequalities
Properties of absolute value inequalities help in solving equations or inequalities involving absolute values by considering cases based on the definition of absolute value. For example, |X| = k implies X = k or X = -k, and understanding these properties aids in correctly setting up and solving the problem.
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