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Ch. 1 - Equations and Inequalities
Chapter 2, Problem 31

In all exercises, other than exercises with no solution, use interval notation to express solution sets and graph each solution set on a number line. In Exercises 27–50, solve each linear inequality. -9x ≥ 36

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1
Start by isolating the variable x. To do this, divide both sides of the inequality by -9. Remember, when you divide or multiply both sides of an inequality by a negative number, you must reverse the inequality sign.
The inequality becomes x ≤ -4 after dividing both sides by -9 and reversing the inequality sign.
Express the solution in interval notation. Since x is less than or equal to -4, the interval notation is (-∞, -4].
To graph the solution on a number line, draw a number line and place a closed circle at -4 to indicate that -4 is included in the solution set.
Shade the number line to the left of -4 to represent all numbers less than or equal to -4.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Linear Inequalities

Linear inequalities are mathematical expressions that involve a linear function and an inequality sign (such as <, >, ≤, or ≥). They represent a range of values rather than a single solution. For example, the inequality -9x ≥ 36 indicates that we are looking for all values of x that satisfy this condition, which can be solved similarly to linear equations but requires special attention to the direction of the inequality.
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Solving Inequalities

To solve a linear inequality, you isolate the variable on one side of the inequality sign, similar to solving an equation. However, if you multiply or divide by a negative number, you must reverse the inequality sign. This process allows you to determine the range of values that satisfy the inequality, which can then be expressed in interval notation.
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Interval Notation

Interval notation is a mathematical notation used to represent a range of values. It uses parentheses and brackets to indicate whether endpoints are included (closed interval) or excluded (open interval). For example, the solution to the inequality -9x ≥ 36 can be expressed in interval notation, which provides a concise way to describe the set of all possible solutions on a number line.
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