1. **Problem vii:** Find the value of $h$ such that the vertex of $f(x) = (x + 4)(x - h)$ has a positive $x$-coordinate.
2. **Step 1:** Expand the function:
$$f(x) = (x + 4)(x - h) = x^2 - hx + 4x - 4h = x^2 + (4 - h)x - 4h$$
3. **Step 2:** The vertex $x$-coordinate of a parabola $ax^2 + bx + c$ is given by:
$$x = -\frac{b}{2a}$$
Here, $a = 1$, $b = 4 - h$.
4. **Step 3:** Substitute $a$ and $b$:
$$x = -\frac{4 - h}{2} = \frac{h - 4}{2}$$
5. **Step 4:** For the vertex to have a positive $x$-coordinate:
$$\frac{h - 4}{2} > 0 \implies h - 4 > 0 \implies h > 4$$
6. **Step 5:** Check the options:
- A: $6 > 4$ (valid)
- B: $4 > 4$ (false)
- C: $-4 > 4$ (false)
- D: $-6 > 4$ (false)
**Answer for vii:** $h = 6$
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7. **Problem viii:** Find the equation of the parabola after transformation $(x,y) \to (x + 4, -3y + 6)$ applied to $y = x^2$.
8. **Step 1:** Original parabola:
$$y = x^2$$
9. **Step 2:** The transformation means:
$$x_{new} = x + 4$$
$$y_{new} = -3y + 6$$
10. **Step 3:** Express $y$ in terms of $x_{new}$:
$$y = (x)^2 = (x_{new} - 4)^2$$
11. **Step 4:** Substitute into $y_{new}$:
$$y_{new} = -3(x_{new} - 4)^2 + 6$$
12. **Step 5:** Rename $x_{new}$ as $x$ for the function notation:
$$f(x) = -3(x - 4)^2 + 6$$
**Answer for viii:** $f(x) = -3(x - 4)^2 + 6$
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**Summary:**
- vii) $h = 6$
- viii) $f(x) = -3(x - 4)^2 + 6$
Vertex Transformation
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