1. **State the problem:** We are given three functions:
$$y = -x + 20$$
$$y = x^2 - 4$$
$$y = 2x + 1$$
We want to analyze these functions and understand their graphs and intersections.
2. **Identify the types of functions:**
- $$y = -x + 20$$ is a linear function with slope $$-1$$ and y-intercept $$20$$.
- $$y = x^2 - 4$$ is a quadratic function (parabola) opening upwards with vertex at $$(0, -4)$$.
- $$y = 2x + 1$$ is a linear function with slope $$2$$ and y-intercept $$1$$.
3. **Find intersections between the parabola and each line:**
**Between $$y = x^2 - 4$$ and $$y = -x + 20$$:**
Set equal:
$$x^2 - 4 = -x + 20$$
Rearranged:
$$x^2 + x - 24 = 0$$
Factor or use quadratic formula:
$$x = \frac{-1 \pm \sqrt{1 + 96}}{2} = \frac{-1 \pm \sqrt{97}}{2}$$
**Between $$y = x^2 - 4$$ and $$y = 2x + 1$$:**
Set equal:
$$x^2 - 4 = 2x + 1$$
Rearranged:
$$x^2 - 2x - 5 = 0$$
Use quadratic formula:
$$x = \frac{2 \pm \sqrt{4 + 20}}{2} = \frac{2 \pm \sqrt{24}}{2} = 1 \pm \sqrt{6}$$
4. **Find intersection between the two lines:**
Set equal:
$$-x + 20 = 2x + 1$$
Rearranged:
$$-x - 2x = 1 - 20$$
$$-3x = -19$$
$$x = \frac{-19}{-3} = \frac{19}{3}$$
Substitute back:
$$y = 2 \times \frac{19}{3} + 1 = \frac{38}{3} + 1 = \frac{41}{3}$$
5. **Summary of intersections:**
- Parabola and $$y = -x + 20$$ intersect at $$x = \frac{-1 \pm \sqrt{97}}{2}$$.
- Parabola and $$y = 2x + 1$$ intersect at $$x = 1 \pm \sqrt{6}$$.
- Lines intersect at $$\left(\frac{19}{3}, \frac{41}{3}\right)$$.
These points can be plotted to visualize the relationships.
**Final answers:**
- Intersection points parabola and $$y = -x + 20$$: $$\left(\frac{-1 + \sqrt{97}}{2}, \frac{1 - \sqrt{97}}{2} + 20\right)$$ and $$\left(\frac{-1 - \sqrt{97}}{2}, \frac{1 + \sqrt{97}}{2} + 20\right)$$.
- Intersection points parabola and $$y = 2x + 1$$: $$\left(1 + \sqrt{6}, 2(1 + \sqrt{6}) + 1\right)$$ and $$\left(1 - \sqrt{6}, 2(1 - \sqrt{6}) + 1\right)$$.
- Intersection point of lines: $$\left(\frac{19}{3}, \frac{41}{3}\right)$$.
Line Parabola Intersections 4Ccf57
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