Mathematics
Grade 8
15 min
Solve one-step inequalities
Solve one-step inequalities
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1
Introduction & Learning Objectives
Learning Objectives
Identify and define key terms related to inequalities.
Solve one-step inequalities involving addition and subtraction.
Solve one-step inequalities involving multiplication and division by positive numbers.
Solve one-step inequalities involving multiplication and division by negative numbers, correctly reversing the inequality sign.
Graph the solution set of a one-step inequality on a number line.
Check solutions to one-step inequalities.
Ever wonder how stores decide how many items to stock, or how much money you can spend without going over budget? 🤔 Inequalities help us figure out "at least" or "at most" situations!
In this lesson, you'll learn how to solve simple inequalities that only require one step. Understanding these wi...
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Key Concepts & Vocabulary
TermDefinitionExample
InequalityA mathematical statement that compares two expressions using an inequality symbol ($<, >, \le, \ge$).$x + 3 < 10$
Solution to an InequalityAny value(s) of the variable that makes the inequality a true statement. Unlike equations, inequalities often have many solutions.For $x < 7$, values like $x=1, 0, -5$ are all solutions.
Graphing an InequalityRepresenting the solution set of an inequality on a number line using open/closed circles and shading.For $x > 3$, an open circle at 3 with shading to the right.
Inverse OperationsOperations that undo each other (e.g., addition undoes subtraction, multiplication undoes division). These are used to isolate the variable.To solve $x - 5 > 2$, you use the inverse operation of adding 5 to both sides.
Va...
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Core Formulas
Addition/Subtraction Property of Inequality
If $a < b$, then $a + c < b + c$ and $a - c < b - c$.
Adding or subtracting the same number from both sides of an inequality does not change the direction of the inequality sign. Use this rule to isolate the variable when a constant is being added to or subtracted from it.
Multiplication/Division Property of Inequality (Positive Number)
If $a < b$ and $c > 0$, then $ac < bc$ and $\frac{a}{c} < \frac{b}{c}$.
Multiplying or dividing both sides of an inequality by the same *positive* number does not change the direction of the inequality sign. Use this rule to isolate the variable when it's multiplied or divided by a positive coefficient.
Multiplication/Division Property of Inequality (Negative Number)...
5 more steps in this tutorial
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Challenging
If a > b and c is a negative number (c < 0), which of the following statements must be true?
A.a + c > b + c
B.a - c > b - c
C.ac < bc
D.a/c > b/c
Challenging
For the inequality -3x ≥ 21, what is the largest integer value of x that is in the solution set?
A.-6
B.-8
C.-7
D.There is no largest integer.
Challenging
A number line graph shows a closed circle on 9 with shading to the left. Which of the following inequalities could have this solution graph?
A.x + 4 ≥ 13
B.x - 5 ≤ 4
C.-2x ≥ -18
D.x/3 > 3
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