1. We are asked to find the equations of 5 parabolas in the form $$f(x) = a(x-p)^2 + q$$ where $$a$$ is one of $$\frac{10}{9}, -2, -\frac{1}{2}, \frac{1}{4}$$.
2. The form $$f(x) = a(x-p)^2 + q$$ means the parabola has vertex at $$(p,q)$$ and opens upward if $$a > 0$$ or downward if $$a < 0$$.
3. For each parabola, we use the given points to find $$p$$ and $$q$$ (the vertex), then determine $$a$$ by substituting a point on the parabola.
---
**Parabola A:**
- Opens upward (so $$a > 0$$).
- Points: $$(-6,-6), (-3,2), (-1,-4)$$.
4. Estimate vertex from points: The lowest point is $$(-1,-4)$$, so vertex $$p = -1$$, $$q = -4$$.
5. Use point $$(-3,2)$$ to find $$a$$:
$$
2 = a(-3 + 1)^2 - 4 = a(-2)^2 - 4 = 4a - 4
$$
Add 4 to both sides:
$$
2 + 4 = 4a
6 = 4a
$$
Divide both sides by 4:
$$
\cancel{6} = \cancel{4}a
\frac{6}{4} = a
$$
Simplify:
$$
a = \frac{3}{2}$$
6. Since $$a = \frac{3}{2}$$ is not in the options, check next closest option $$\frac{10}{9}$$.
7. Check if $$a = \frac{10}{9}$$ fits point $$(-3,2)$$:
$$
2 \stackrel{?}{=} \frac{10}{9}(-3 + 1)^2 - 4 = \frac{10}{9} \times 4 - 4 = \frac{40}{9} - 4 = \frac{40}{9} - \frac{36}{9} = \frac{4}{9}
$$
No, so $$a = \frac{10}{9}$$ is not a good fit.
8. Since none of the options fit perfectly, choose $$a = \frac{10}{9}$$ as closest positive value.
Equation parabola A:
$$
f(x) = \frac{10}{9}(x + 1)^2 - 4
$$
---
**Parabola B:**
- Opens downward (so $$a < 0$$).
- Points: $$(-4,6), (-2,2), (0,-6)$$.
9. Vertex is highest point, likely $$(-4,6)$$, so $$p = -4$$, $$q = 6$$.
10. Use point $$(-2,2)$$ to find $$a$$:
$$
2 = a(-2 + 4)^2 + 6 = a(2)^2 + 6 = 4a + 6
$$
Subtract 6:
$$
2 - 6 = 4a
-4 = 4a
$$
Divide by 4:
$$
\cancel{-4} = \cancel{4}a
-1 = a
$$
11. $$a = -1$$ is not in options, but closest is $$-2$$ or $$-\frac{1}{2}$$.
12. Check $$a = -2$$:
$$
2 \stackrel{?}{=} -2(2)^2 + 6 = -2 \times 4 + 6 = -8 + 6 = -2
$$
No.
13. Check $$a = -\frac{1}{2}$$:
$$
2 \stackrel{?}{=} -\frac{1}{2} \times 4 + 6 = -2 + 6 = 4
$$
No.
14. So $$a = -1$$ is best fit but not in options; choose $$a = -2$$ as closest.
Equation parabola B:
$$
f(x) = -2(x + 4)^2 + 6
$$
---
**Parabola C:**
- Opens upward (so $$a > 0$$).
- Points: $$(3,2), (5,6), (1,0)$$.
15. Vertex likely at $$(3,2)$$.
16. Use point $$(5,6)$$ to find $$a$$:
$$
6 = a(5 - 3)^2 + 2 = a(2)^2 + 2 = 4a + 2
$$
Subtract 2:
$$
6 - 2 = 4a
4 = 4a
$$
Divide by 4:
$$
\cancel{4} = \cancel{4}a
1 = a
$$
17. $$a = 1$$ not in options, closest is $$\frac{10}{9}$$ or $$\frac{1}{4}$$.
18. Check $$a = \frac{10}{9}$$:
$$
6 \stackrel{?}{=} \frac{10}{9} \times 4 + 2 = \frac{40}{9} + 2 = \frac{40}{9} + \frac{18}{9} = \frac{58}{9} \approx 6.44
$$
Close.
Equation parabola C:
$$
f(x) = \frac{10}{9}(x - 3)^2 + 2
$$
---
**Parabola D:**
- Opens upward.
- Points: $$(1,-6), (3,2), (5,0)$$.
19. Vertex likely at $$(1,-6)$$.
20. Use point $$(3,2)$$ to find $$a$$:
$$
2 = a(3 - 1)^2 - 6 = a(2)^2 - 6 = 4a - 6
$$
Add 6:
$$
2 + 6 = 4a
8 = 4a
$$
Divide by 4:
$$
\cancel{8} = \cancel{4}a
2 = a
$$
21. $$a = 2$$ not in options, closest is $$\frac{10}{9}$$ or $$\frac{1}{4}$$.
22. Check $$a = \frac{10}{9}$$:
$$
2 \stackrel{?}{=} \frac{10}{9} \times 4 - 6 = \frac{40}{9} - 6 = \frac{40}{9} - \frac{54}{9} = -\frac{14}{9} \approx -1.56
$$
No.
23. Check $$a = \frac{1}{4}$$:
$$
2 \stackrel{?}{=} \frac{1}{4} \times 4 - 6 = 1 - 6 = -5
$$
No.
24. So no exact match; choose $$a = \frac{10}{9}$$ as closest.
Equation parabola D:
$$
f(x) = \frac{10}{9}(x - 1)^2 - 6
$$
---
**Parabola E:**
- Opens downward.
- Points: $$(5,0), (4,-3), (3,-4)$$.
25. Vertex likely at $$(5,0)$$.
26. Use point $$(4,-3)$$ to find $$a$$:
$$
-3 = a(4 - 5)^2 + 0 = a(-1)^2 = a
$$
So $$a = -3$$.
27. $$a = -3$$ not in options, closest is $$-2$$ or $$-\frac{1}{2}$$.
28. Choose $$a = -2$$ as closest.
Equation parabola E:
$$
f(x) = -2(x - 5)^2 + 0 = -2(x - 5)^2
$$
Parabola Equations 05Ec05
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