Math

Inequality to Interval Notation Calculator

Solve a linear inequality ax + b ≷ c and write the interval.

Operator

Calculated Output

x boundary 4

Interval (-∞, 4)

Formula: Isolate x; flip the sign if dividing by a negative

Step-by-Step Breakdown

1. Values used:

2. a = 2

3. b = 1

4. c = 9

6. x boundary = 4

7. Interval = (-∞, 4)

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The math behind it

Isolate x just like an equation, but remember to flip the inequality sign whenever you multiply or divide by a negative number.

2x + 1 < 9 → x < 4 → (−∞, 4).

When does the sign flip?

Only when you multiply or divide both sides by a negative value.