Chapter 8: Problem 52
Graph the solution set, and write it using interval notation. $$ -15<3 x+6<-12 $$
Short Answer
Expert verified
(-7, -6)
Step by step solution
01
- Isolate the variable
The first step is to isolate the variable, which is \(x\) in this case. Start by solving the compound inequality \(-15 < 3x + 6 < -12\). To do this, subtract 6 from all parts of the inequality:-15 - 6 < 3x + 6 - 6 < -12 - 6This simplifies to:-21 < 3x < -18
02
- Further isolate \(x\)
Next, we divide each part of the inequality by 3 to solve for \(x\):\frac{-21}{3} < \frac{3x}{3} < \frac{-18}{3} This simplifies to:-7 < x < -6
03
- Write the solution in interval notation
The inequality \(-7 < x < -6\) can be written in interval notation as follows: (-7, -6)
04
- Graph the solution
To graph the solution set, draw a number line and shade the region between -7 and -6 (not including -7 and -6, since the inequalities are strict). Place open circles at -7 and -6 to show that these points are not included in the solution set.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Interval Notation
Understanding interval notation helps you express the range of solutions in a compact form. In our compound inequality \[ -7 < x < -6 \], we see that the solution is the set of all numbers between -7 and -6, but not including -7 and -6 themselves. This is because the inequality signs are strict (<), meaning these endpoints are not part of the solution.
To write this in interval notation, use parentheses:
To write this in interval notation, use parentheses:
- A parenthesis \( ( \) or \( ) \) means that the endpoint is not included.
- A bracket \( [ \) or \( ] \) means that the endpoint is included.
Number Line Graphing
Graphing the solution set on a number line is a visual method to understand the range of values that satisfy the inequality. For \[ -7 < x < -6 \], you'll follow these steps:
- Draw a horizontal line to represent the number line.
- Mark the points -7 and -6 on the number line.
- Place open circles at -7 and -6 to show that these points are not included.
- Shade the region between -7 and -6.
Isolating Variables
Isolating the variable is a fundamental step in solving inequalities, ensuring that you solve for the variable correctly. Here, we start with the inequality \-15 < 3x + 6 < -12\. The goal is to isolate \( x \). Follow these steps:
The isolation process is not just about getting the variable alone but ensuring every step respects the inequality rules to maintain solution integrity.
- First, subtract 6 from all parts of the inequality: \( -15-6 < 3x + 6 - 6 < -12 - 6 \). This simplifies to \( -21 < 3x < -18 \).
- Next, divide each part by 3 to solve for x: \[ \frac{-21}{3} < \frac{3x}{3} < \frac{-18}{3} \]. This simplifies to \[-7 < x < -6 \].
The isolation process is not just about getting the variable alone but ensuring every step respects the inequality rules to maintain solution integrity.