Chapter 3: Problem 26
Find the values of \(x\) that solve the inequality. $$|1-4 x|>7$$
Short Answer
Expert verified
The solution is \(x < -\frac{3}{2}\) or \(x > 2\).
Step by step solution
01
Understand the Absolute Value Inequality
The inequality \(|1-4x| > 7\) means the absolute value of \(1-4x\) is greater than 7. Recall that for an absolute value inequality like \(|A| > B\), the solution is found from two inequalities: \(A > B\) or \(A < -B\).
02
Set Up the First Inequality
Set up the first inequality by removing the absolute value: \(1 - 4x > 7\).
03
Solve the First Inequality
Start by solving \(1 - 4x > 7\):Subtract 1 from each side:\[-4x > 6\]Divide both sides by \(-4\), remembering to reverse the inequality sign:\[x < -\frac{3}{2}\]
04
Set Up the Second Inequality
Set up the second inequality from the absolute value: \(1 - 4x < -7\).
05
Solve the Second Inequality
Solve \(1 - 4x < -7\):Subtract 1 from each side:\[-4x < -8\]Divide both sides by \(-4\), reversing the inequality sign:\[x > 2\]
06
Combine the Solutions
The solutions to the inequalities \(1 - 4x > 7\) and \(1 - 4x < -7\) combine to give two separate ranges, which do not overlap. Thus, the solution to the original inequality \(|1 - 4x| > 7\) is \(x < -\frac{3}{2}\) or \(x > 2\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Absolute Value
The absolute value of a number is its distance from zero on the number line, regardless of direction. It is a measure of magnitude without regard to sign. For any real number \(A\), the absolute value is denoted by \(|A|\) and is defined as:
- \(|A| = A\) if \(A \geq 0\)
- \(|A| = -A\) if \(A < 0\)
Inequality Solution
Solving inequalities requires careful manipulation of expressions, often similar to solving equations but with special attention to the direction of the inequality sign. For the inequality \(|1-4x| > 7\), we consider two separate linear inequalities:
- First inequality: \(1-4x > 7\)
- Second inequality: \(1-4x < -7\)
- Subtract constants from both sides.
- Divide or multiply coefficients of \(x\), being mindful to reverse the inequality sign when multiplying or dividing by a negative number.
Inequalities in Mathematics
Inequalities are expressions that show the relative size or order of two values. Unlike equations, they describe a range of possible solutions. There are four primary inequality symbols:
- Greater than: \(>\)
- Less than: \(<\)
- Greater than or equal to: \(\geq\)
- Less than or equal to: \(\leq\)
Compound Inequalities
Compound inequalities link two or more inequalities together, often indicating a range of solutions. They can be described using the word "or" (disjunction) or "and" (conjunction). For an inequality of the form \(|1-4x|>7\), we separate it into two parts:
- \(x < -\frac{3}{2}\) or
- \(x > 2\)