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Solving Linear Inequalities and Interval Notation

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Linear Inequalities and Interval Notation

Introduction to Linear Inequalities

Linear inequalities are mathematical statements that compare linear expressions using inequality symbols such as >, <, ≥, and ≤. The solution to a linear inequality is a set of values that make the inequality true, often represented on a number line and using interval notation.

Solving and Representing Linear Inequalities

  • Standard Notation: The inequality is written using symbols (e.g., x > 2).

  • Number Line Representation: Solutions are shown as arrows or shaded regions on a number line, indicating which values of x satisfy the inequality.

  • Interval Notation: Solutions are expressed as intervals, using parentheses ( ) for open endpoints and brackets [ ] for closed endpoints.

Examples and Interval Notation

Inequality (Standard Notation)

Number Line Representation

Interval Notation

x > 2

Arrow to the right from 2 (open circle)

(2, infty)

x < 2

Arrow to the left from 2 (open circle)

(-infty, 2)

x ≥ 2

Arrow to the right from 2 (closed circle)

[2, infty)

x ≤ 2

Arrow to the left from 2 (closed circle)

(-infty, 2]

-2 < x < 2

Arrow between -2 and 2 (open circles)

(-2, 2)

-2 ≤ x ≤ 2

Arrow between -2 and 2 (closed circles)

[-2, 2]

Key Concepts and Definitions

  • Open Interval: means all values between a and b, not including endpoints.

  • Closed Interval: means all values between a and b, including endpoints.

  • Infinity: is always paired with a parenthesis, never a bracket, because infinity is not a specific number.

  • Compound Inequality: An inequality that combines two statements, such as .

Extra Notes

  • Intervals ending in : Use a parenthesis, e.g., .

  • Intervals starting with : Use a parenthesis, e.g., .

  • Compound inequalities: Represented as intervals, e.g., is .

Application Example

  • Example: Solve and write the solution in interval notation. Solution: The solution is all real numbers greater than or equal to 3. Interval Notation:

Additional info: Interval notation is a concise way to describe sets of numbers and is widely used in algebra to express solution sets for inequalities.

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