Let's solve each problem step by step using the
vertex form of a quadratic function:
Vertex Form:
$$
y = a(x - h)^2 + k
$$
-
Vertex: $(h, k)$
-
Axis of Symmetry (A.O.S.): $x = h$
- If $a > 0$: parabola opens
upward, vertex is a
minimum
- If $a < 0$: parabola opens
downward, vertex is a
maximum
---
1. $ y = (x - 1)^2 + 2 $
- Compare to $ y = a(x - h)^2 + k $
- $ a = 1 $, $ h = 1 $, $ k = 2 $
-
Vertex: $ (1, 2) $
-
A.O.S.: $ x = 1 $
- Since $ a = 1 > 0 $ → opens
up, so vertex is a
minimum
✔ Answer:
- Vertex = $ (1, 2) $
- A.O.S. = $ x = 1 $
- Min
---
2. $ y = 2(x - 2)^2 + 5 $
- $ a = 2 $, $ h = 2 $, $ k = 5 $
-
Vertex: $ (2, 5) $
-
A.O.S.: $ x = 2 $
- $ a = 2 > 0 $ → opens
up, so vertex is a
minimum
✔ Answer:
- Vertex = $ (2, 5) $
- A.O.S. = $ x = 2 $
- Min
---
3. $ y = -3(x + 7)^2 - 8 $
Note: $ x + 7 = x - (-7) $, so $ h = -7 $
- $ a = -3 $, $ h = -7 $, $ k = -8 $
-
Vertex: $ (-7, -8) $
-
A.O.S.: $ x = -7 $
- $ a = -3 < 0 $ → opens
down, so vertex is a
maximum
✔ Answer:
- Vertex = $ (-7, -8) $
- A.O.S. = $ x = -7 $
- Max
---
4. $ y = (x - 5)^2 - 3 $
- $ a = 1 $, $ h = 5 $, $ k = -3 $
-
Vertex: $ (5, -3) $
-
A.O.S.: $ x = 5 $
- $ a = 1 > 0 $ → opens
up, so vertex is a
minimum
✔ Answer:
- Vertex = $ (5, -3) $
- A.O.S. = $ x = 5 $
- Min
---
Summary Table:
| Problem | Function | Vertex | A.O.S. | Max or Min |
|--------|---------|--------|--------|------------|
| 1 | $ y = (x - 1)^2 + 2 $ | $ (1, 2) $ | $ x = 1 $ | Min |
| 2 | $ y = 2(x - 2)^2 + 5 $ | $ (2, 5) $ | $ x = 2 $ | Min |
| 3 | $ y = -3(x + 7)^2 - 8 $ | $ (-7, -8) $ | $ x = -7 $ | Max |
| 4 | $ y = (x - 5)^2 - 3 $ | $ (5, -3) $ | $ x = 5 $ | Min |
---
Graphing Tips (for sketching):
- Plot the
vertex.
- Use the
axis of symmetry as a guide.
- Pick a few $ x $-values on either side of the vertex, plug into the equation, and plot points.
- Reflect across the A.O.S.
- Draw a smooth U-shaped curve.
For example, for #1:
- Vertex: $ (1, 2) $
- Try $ x = 0 $: $ y = (0 - 1)^2 + 2 = 1 + 2 = 3 $
- Try $ x = 2 $: $ y = (2 - 1)^2 + 2 = 1 + 2 = 3 $
- So points: $ (0, 3), (1, 2), (2, 3) $ — symmetric!
Repeat similarly for others.
Let me know if you'd like the graphs sketched out!
Parent Tip: Review the logic above to help your child master the concept of graphing parabolas worksheet.