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Solve the related quadratic equation, plot the solutions on a number line, and test a value from each interval.
{ x| - 1 < x < 2 }
To solve the quadratic inequality algebraically, we will follow three steps.
We will start by solving the related equation.
2=x^2-x ⇔ - 1x^2+ 1x+ 2=0
Substitute values
Calculate root
Now we can calculate the first root using the positive sign and the second root using the negative sign.
| x=- 1 ± 3/- 2 | |
|---|---|
| x=- 1 + 3/- 2 | x=- 1 - 3/- 2 |
| x=2/- 2 | x=- 4/- 2 |
| x= - 1 | x= 2 |
The solutions of the related equation are - 1 and 2. Let's plot them on a number line. Since the original is a strict inequality, the points will be open.
Finally, we must test a value from each interval to see if it satisfies the original inequality. Let's choose a value from the first interval, x < - 1. For simplicity, we will choose x=- 2.
Since x=- 2 did not produce a true statement, the interval x < - 1 is not part of the solution. Similarly, we can test the other two intervals.
| Interval | Test Value | Statement | Is It Part of the Solution? |
|---|---|---|---|
| - 1 < x < 2 | 0 | 2 > 0 ✓ | Yes |
| x > 2 | 3 | 2 ≯ 6 * | No |
We can now write the solution set and show it on a number line. { x| - 1 < x < 2 } or (- 1, 2)