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What is a Simultaneous Inequality?

Published in Algebra 2 mins read

A simultaneous inequality is a set of two or more inequalities that must be solved together, meaning the solution must satisfy all the inequalities in the set at the same time.

Understanding Simultaneous Inequalities

Essentially, when dealing with simultaneous inequalities, you're looking for the range of values that make all the inequalities true. The inequalities involve the same variable(s), creating a system where their solutions intersect or overlap.

Example

Consider the following system of inequalities:

  • x > 2
  • x < 5

This is a simultaneous inequality. The solution is all values of x that are greater than 2 and less than 5. We can write this as 2 < x < 5.

Solving Simultaneous Inequalities

  1. Solve each inequality individually: Find the solution set for each inequality as if it were the only one.
  2. Find the intersection: Determine the values that satisfy all the inequalities. This is often visualized on a number line or coordinate plane. The intersection of the solution sets is the solution to the simultaneous inequality.

Representing the Solution

The solution to a simultaneous inequality can be expressed in several ways:

  • Inequality Notation: As seen in the example above (2 < x < 5).
  • Interval Notation: (2, 5) - This represents all numbers between 2 and 5, not including 2 and 5. If the inequalities included "or equal to", square brackets would be used, e.g., [2, 5].
  • Graphically: By shading the region on a number line or coordinate plane that satisfies all inequalities.

More Complex Examples

Simultaneous inequalities can also involve more complex expressions, such as:

  • -3 ≤ 2x + 1 < 7 (This is actually two inequalities: -3 ≤ 2x + 1 and 2x + 1 < 7)
  • Systems of inequalities with two variables, such as:
    • y > x + 1
    • y < -x + 3

In these cases, solving involves algebraic manipulation and/or graphing to find the region that satisfies all conditions.

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