Chapter 1: Problem 27
Solve the linear inequality. Express the solution using interval notation and graph the solution set. $$ 2 \leq x+5<4 $$
Short Answer
Expert verified
The solution is \([-3, -1)\) and can be graphed with a solid dot at \(-3\) and an open dot at \(-1\).
Step by step solution
01
Understand the Compound Inequality
The given inequality is compound: \(2 \leq x+5 < 4\). This means we have two conditions that \(x\) must satisfy simultaneously: \(2 \leq x+5\) and \(x+5 < 4\). We will solve each inequality separately.
02
Solve the First Inequality
First, we solve \(2 \leq x+5\). Subtract 5 from both sides to isolate \(x\): \[2 - 5 \leq x+5 - 5\]\[-3 \leq x\].
03
Solve the Second Inequality
Now, we solve \(x+5 < 4\). Subtract 5 from both sides to isolate \(x\): \[x+5 - 5 < 4 - 5\]\[x < -1\].
04
Combine the Solutions
The solutions to the compound inequality are both conditions satisfied simultaneously: \(-3 \leq x < -1\). This is the interval for which the inequality holds true.
05
Express the Solution in Interval Notation
In interval notation, the solution \(-3 \leq x < -1\) is expressed as \([-3, -1)\). The interval uses a square bracket \([\) for \(-3\) because it's included and a parenthesis \()\) for \(-1\) because it's not included.
06
Graph the Solution Set
To graph the solution set on a number line, draw a solid dot at \(-3\) to indicate it is included in the solution. Use an open dot at \(-1\) to show that it is not included. Shade the region between \(-3\) and \(-1\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Compound Inequalities
A compound inequality is essentially two inequalities combined into one statement by using either "and" or "or". It helps us find the range of solutions for a variable that satisfies multiple conditions at the same time. In our example, we were given the inequality \(2 \leq x+5 < 4\). Here, the two inequalities \(2 \leq x+5\) and \(x+5 < 4\) must both be true for \(x\) to be a valid solution. The word "and" is implicit, meaning solutions must satisfy both conditions. Working with compound inequalities is beneficial when you need to locate a range that suits specific criteria.
Interval Notation
Interval notation is a concise way to describe a set of numbers along a number line. In this notation, a pair of numbers are written as an interval, representing all numbers between them. Based on our solved inequality \(-3 \leq x < -1\), let's see how interval notation works:
- \([-3, -1)\) is read as "from -3 to just below -1".
- The square bracket \([\) on \(-3\) means -3 is included in the solution.
- The parenthesis \()\) on \(-1\) shows -1 is not included.
Number Line Graphing
Graphing inequalities on a number line is a helpful visual tool to quickly identify which parts of the number line are included in an inequality's solution:
- In our example, the solution \([-3, -1)\) is depicted by shading the area between -3 and -1.
- A solid dot at \(-3\) indicates that -3 is part of the solution, as it satisfied \(-3 \leq x\).
- An open dot at \(-1\) indicates -1 is not part of the solution, reflecting the "less than" part \(x < -1\).
Solving Inequalities
Solving inequalities is much like solving equations but requires a keen attention to inequality signs and the rules they entail. Here's how we solve them step-by-step:
- When tackling each inequality, isolate the variable on one side to determine its range of values.
- For \(2 \leq x+5\), subtract 5 from both sides to get \(-3 \leq x\). This tells us \(x\) can be -3 or any larger number.
- For \(x+5 < 4\), subtract 5 to determine \(x < -1\). This sets an upper boundary for \(x\).
- Combine these solutions. The intersection, or overlapping part of both sets, provides the valid solution: \(-3 \leq x < -1\).