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Solve the related quadratic equation, plot the solutions on a number line, and test a value from each interval.
{x| - 1.693 < x < 0.443 }
To solve the quadratic inequality algebraically, we will follow three steps.
We will start by solving the related equation.
4x^2-3 < - 5x ⇔ 4x^2+ 5x+( -3)<0
Substitute values
Now we can calculate the first root using the positive sign and the second root using the negative sign.
| x=- 5±sqrt(73)/8 | |
|---|---|
| x=-5+ sqrt(73)/8 | x=-5- sqrt(73)/8 |
| x=- 5/8+sqrt(73)/8 | x=- 5/8-sqrt(73)/8 |
| x≈ 0.443 | x≈ -1.693 |
The solutions of the related equation are approximately 0.443 and -1.693. 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 < - 1.693. For simplicity, we will choose x=- 2.
x= - 2
Calculate power
Multiply
Add and subtract terms
Since x=- 2 did not produce a true statement, the interval x < - 1.693 is not part of the solution. Similarly, we can test the other two intervals.
| Interval | Test Value | Statement | Is It Part of the Solution? |
|---|---|---|---|
| x < - 1.693 | -2 | 3 ≮ 0 * | No |
| - 1.693 < x < 0.443 | 0 | -3 < 0 ✓ | Yes |
| x > 0.443 | 1 | 6 ≮ 0 * | No |
We can now write the solution set and show it on a number line. {x| - 1.693 < x < 0.443}