5. Quadratic Inequalities
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Solve the related quadratic equation, plot the solutions on a number line, and test a value from each interval.
{ x| x ≤ - 5.19 or x ≥ 0.19 }
To solve the quadratic inequality algebraically, we will follow three steps.
Substitute values
| x=- 5±sqrt(29)/2 | |
|---|---|
| x=- 5 + sqrt(29)/2 | x=- 5 - sqrt(29)/2 |
| x=- 5/2+sqrt(29)/2 | x=- 5/2-sqrt(29)/2 |
| x≈ 0.19 | x≈ - 5.19 |
The solutions of the related equation are approximately - 5.19 and 0.19. Let's plot them on a number line. Since the original is not a strict inequality, the points will be closed.
| Interval | Test Value | Statement | Is It Part of the Solution? |
|---|---|---|---|
| - 5.19 ≥ x ≥ 0.19 | 0 | - 1 ≥ 0 * | No |
| x≥ 0.19 | 1 | - 1 ≥ - 6 ✓ | Yes |
We can now write the solution set and show it on a number line. { x| x ≤ - 5.19 or x ≥ 0.19 } or (- ∞, - 5.19] ⋃ [0.19, ∞)