Chapter 2: Problem 69
An equation of the form \(|f(x)|=|g(x)|\) is given. (a) Solve the equation analytically and support the solution graphically. (b) Solve \(|f(x)|>|g(x)|\) (c) Solve \(|f(x)|<|g(x)|\) $$|-2 x+5|=|x+3|$$
Short Answer
Expert verified
Solutions: (a) \(x = \frac{2}{3}, 8\); (b) \((-\infty, \frac{2}{3}) \cup (8, \infty)\); (c) \((\frac{2}{3}, 8)\)."
Step by step solution
01
Remove Absolute Values
Given the equation \(|-2x + 5| = |x + 3|\), we need to address this by considering the two cases enabled by absolute values: one where both expressions are non-negative and one where both are non-positive. The two cases mean 1. a)\(-2x + 5 = x + 3\) b) \(-2x + 5 = -(x + 3)\)
02
Solve the First Case
For the first case, solve \(-2x + 5 = x + 3\):Subtract \(x\) from both sides:\(-2x - x + 5 = 3\)Combine like terms:\(-3x + 5 = 3\)Subtract 5 from both sides:\(-3x = -2\)Divide by \(-3\):\(x = \frac{2}{3}\).
03
Solve the Second Case
For the second case, solve \(-2x + 5 = -(x + 3)\):Distribute the negative sign on the right side:\(-2x + 5 = -x - 3\)Add \(2x\) to both sides to combine terms:\(5 = x - 3\)Add 3 to both sides:\(x = 8\).
04
Verify Solutions with Original Expression
Verify whether the solutions \(x = \frac{2}{3}\) and \(x = 8\) satisfy the original absolute value equation. Substitute back into \(|-2x + 5|\) and \(|x + 3|\):For \(x = \frac{2}{3}\):\(|-2(\frac{2}{3}) + 5| = |\frac{2}{3} + 3|\)Both sides simplify to equal amounts.For \(x = 8\):\(|-2(8) + 5| = |8 + 3|\)Both sides also simplify to equal amounts.
05
Analyze Inequality \(|-2x + 5| > |x + 3|\)
Consider both cases for the inequality:1. \(-2x + 5 > x + 3\)Solve by subtracting \(x\) and simplifying:\(-3x > -2\) Divide by \(-3\), flip inequality: \(x < \frac{2}{3}\).2. \(-x - 3 > -2x + 5\)Rearrange and solve:\(x > 8\).
06
Analyze Inequality \(|-2x + 5| < |x + 3|\)
Consider both cases for the inequality:1. \(-2x + 5 < x + 3\)Solve by subtracting \(x\): \(-3x < -2\)Divide by \(-3\), flip inequality: \(x > \frac{2}{3}\).2. \(-x - 3 < -2x + 5\)Rearrange: \(x < 8\).
07
Combine Results for Inequalities
Combine the solutions found to problem into intervals based on the inequalities.For \(|-2x + 5| > |x + 3|\), combine overlapping intervals:The solution is \((-\infty, \frac{2}{3}) \cup (8, \infty)\).For \(|-2x + 5| < |x + 3|\), the intersection of solutions gives:The solution is \((\frac{2}{3}, 8)\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Inequality Solutions
When dealing with absolute value equations like \(|-2x + 5| = |x + 3|\), it's essential to understand how inequalities can arise and be solved. Absolute values can create two separate inequalities based on whether the expressions inside are positive or negative. For example, \(|-2x + 5| > |x + 3|\) leads to two cases: \(-2x + 5 > x + 3\) and \(-x - 3 > -2x + 5\). Solving these separately involves rearranging terms and isolating \(x\). Remember, dividing or multiplying by a negative reverses the inequality sign.\
- For \(-2x + 5 > x + 3\), solving leads to \(x < \frac{2}{3}\).
- For \(-x - 3 > -2x + 5\), solving results in \(x > 8\).
Graphical Representation
Graphing absolute value equations and inequalities can provide a visual intuition of the solution. For \(|-2x + 5| = |x + 3|\), you're essentially looking at the intersections of two V-shaped graphs. The graphs of \(|-2x + 5|\) and \(|x + 3|\) will intersect at points where the solutions lie, providing a visual reference for where the two expressions are equal.
- Draw the graphs of both expressions on a coordinate plane.
- The intersection points represent the solutions \(x = \frac{2}{3}\) and \(x = 8\).
Analytical Methods
Analytically solving absolute value equations like \(|-2x + 5|=|x + 3|\) involves considering both scenarios: one where both terms are equal in magnitude but opposite in sign, and one where they are equal.
- Break down the equation into two cases: \-2x + 5 = x + 3\ and \-2x + 5 = -(x + 3)\.
- Solve each equation separately. The solutions \(x = \frac{2}{3}\) and \(x = 8\) are found.