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 < 0.61 or x> 2.72 }
To solve the quadratic inequality algebraically, we will follow three steps.
Substitute values
| x=- 10±sqrt(40)/- 6 | |
|---|---|
| x=- 10 + sqrt(40)/- 6 | x=- 10 - sqrt(40)/- 6 |
| x=- 10/- 6+sqrt(40)/- 6 | x=- 10/- 6-sqrt(40)/- 6 |
| x=10/6-sqrt(40)/6 | x=10/6+sqrt(40)/6 |
| x≈ 0.61 | x≈ 2.72 |
The solutions of the related equation are approximately 0.61 and 2.72. Let's plot them on a number line. Since the original is a strict inequality, the points will be open.
| Interval | Test Value | Statement | Is It Part of the Solution? |
|---|---|---|---|
| 0.61 < x < 2.72 | 1 | 7 ≮ 5 * | No |
| x > 2.72 | 3 | 3 < 5 ✓ | Yes |
We can now write the solution set and show it on a number line. { x| x < 0.61 or x> 2.72 } or (- ∞, 0.61) ⋃ (2.72, ∞)