1. **State the problem:** Graph the parabola given by the equation $$y = -x^2 + 2x + 8$$ and plot 5 points including the roots and the vertex.
2. **Formula and rules:** The equation is a quadratic function in standard form $$y = ax^2 + bx + c$$ where $$a = -1$$, $$b = 2$$, and $$c = 8$$.
- The parabola opens downward because $$a < 0$$.
- The vertex formula is $$x = -\frac{b}{2a}$$.
- Roots are found by solving $$y=0$$.
3. **Find the vertex:**
$$x = -\frac{2}{2 \times (-1)} = -\frac{2}{-2} = 1$$
Substitute $$x=1$$ into the equation:
$$y = -(1)^2 + 2(1) + 8 = -1 + 2 + 8 = 9$$
Vertex is at $$(1, 9)$$.
4. **Find the roots:** Solve $$-x^2 + 2x + 8 = 0$$
Multiply both sides by $$-1$$ to simplify:
$$\cancel{-1} \times (-x^2 + 2x + 8) = \cancel{-1} \times 0$$
$$x^2 - 2x - 8 = 0$$
Factor:
$$(x - 4)(x + 2) = 0$$
Roots are $$x = 4$$ and $$x = -2$$.
5. **Find symmetric points:** Since the vertex is at $$x=1$$, points equidistant from 1 have the same $$y$$.
At $$x=0$$:
$$y = -(0)^2 + 2(0) + 8 = 8$$
At $$x=2$$:
$$y = -(2)^2 + 2(2) + 8 = -4 + 4 + 8 = 8$$
6. **Summary of points to plot:**
- Roots: $$(-2, 0)$$ and $$(4, 0)$$
- Vertex: $$(1, 9)$$
- Symmetric points: $$(0, 8)$$ and $$(2, 8)$$
These 5 points define the parabola shape.
**Final answer:** The parabola opens downward with vertex at $$(1, 9)$$, roots at $$(-2, 0)$$ and $$(4, 0)$$, and symmetric points at $$(0, 8)$$ and $$(2, 8)$$.
Graph Parabola 5B857E
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