Chapter 2: Problem 82
Solve and graph the solution set. In addition, present the solution set in interval notation. $$ -10 x-3 \leq 17 \text { or } 20 x-6>-26 $$
Short Answer
Expert verified
The solution in interval notation is [-2, ∞).
Step by step solution
01
Solve the First Inequality
We are given \[-10x - 3 \leq 17.\] To solve for \(x\), we first add 3 to both sides, giving us:\[-10x \leq 20.\] Next, we divide both sides by -10. Remember to flip the inequality sign because we are dividing by a negative number:\[x \geq -2.\]
02
Solve the Second Inequality
The second inequality is \[20x - 6 > -26.\]Add 6 to both sides to isolate the term with \(x\):\[20x > -20.\]Now, divide both sides by 20:\[x > -1.\]
03
Combine the Inequalities
The first inequality, \(x \geq -2\), represents all \(x\) values that are greater than or equal to -2. The second inequality, \(x > -1\), represents all \(x\) values that are greater than -1. Since this is an "or" inequality, we take the union of both solutions, meaning we include all values from both solutions:\(x \geq -2\) OR \(x > -1\).
04
Graph the Solution Set
Draw a number line. To represent \(x \geq -2\), draw a solid dot at -2 and shade to the right. For \(x > -1\), draw an open dot at -1 (because -1 is not included) and also shade to the right. The entire region from \(-2\) to infinity will be shaded.
05
Write the Interval Notation
In interval notation, the solution \(x \geq -2\) OR \(x > -1\) is written as:\[[-2, \infty).\]This interval includes all numbers greater than or equal to -2.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Solving Inequalities
Solving inequalities is a fundamental skill in algebra that helps us find a range of possible values for a variable. Inequalities use symbols such as \(>\), \(<\), \(\geq\), and \(\leq\) to show that one side is greater or smaller than the other.
To solve an inequality:
In this exercise, two inequalities were solved. For \(-10x - 3 \leq 17\), we added 3, then divided by -10 (flipping the inequality) to get \(x \geq -2\). In the second inequality, \(20x - 6 > -26\), we added 6 and divided by 20 to get \(x > -1\). Understanding each step ensures a strong grasp of solving inequalities!
To solve an inequality:
- Perform arithmetic operations similar to those in equations—addition, subtraction, multiplication, or division—to isolate the variable.
- Remember to flip the inequality sign whenever you multiply or divide by a negative number. This is because dividing by a negative reverses the order of the inequality.
- Solve each part of a compound inequality separately, if needed, then combine the solutions logically (using "and" or "or").
In this exercise, two inequalities were solved. For \(-10x - 3 \leq 17\), we added 3, then divided by -10 (flipping the inequality) to get \(x \geq -2\). In the second inequality, \(20x - 6 > -26\), we added 6 and divided by 20 to get \(x > -1\). Understanding each step ensures a strong grasp of solving inequalities!
Interval Notation
Once you solve an inequality, you express its solution using interval notation. This is a way to write subsets of the real number line.
Interval notation uses:
In the provided solution, the combined inequalities \(x \geq -2\) or \(x > -1\) were expressed in interval notation as \([-2, \infty)\). This notation succinctly captures all numbers from -2 to infinity, with -2 included.
Interval notation uses:
- Brackets [ ] to include endpoints if the inequality is a greater than or equal to (\(\geq\)) or less than or equal to (\(\leq\)).
- Parentheses ( ) to exclude endpoints when the inequality is strictly greater than (>) or less than (<).
- The symbol \( \infty \) or \(-\infty\) to signify unbounded ranges, remembering \(\infty\) is never included, so it's always paired with a parenthesis.
In the provided solution, the combined inequalities \(x \geq -2\) or \(x > -1\) were expressed in interval notation as \([-2, \infty)\). This notation succinctly captures all numbers from -2 to infinity, with -2 included.
Graphing Solution Sets
Graphing solution sets visually represents the solutions of inequalities on a number line, helping to clarify and check your work. To graph an inequality:
For the example here, we graph \(x \geq -2\) with a solid dot at -2 and \(x > -1\) with an open dot at -1, shading to the right to show all valid solutions. The graph makes it clear that all numbers from -2 onward are part of the solution set, visualizing the logic behind combining the inequalities.
- Draw a number line with appropriate values marked.
- Use a solid dot to include a number (for \(\geq\) or \(\leq\) inequalities) or an open dot to exclude it (for > or <).
- Shade the area to the right for greater than solutions or to the left for less than solutions.
For the example here, we graph \(x \geq -2\) with a solid dot at -2 and \(x > -1\) with an open dot at -1, shading to the right to show all valid solutions. The graph makes it clear that all numbers from -2 onward are part of the solution set, visualizing the logic behind combining the inequalities.