1. **State the problem:** Find the minimum point of the graph of $f(x) = x^2 - 4x + 9$.
2. To find the minimum point of a quadratic function $f(x) = ax^2 + bx + c$ (with $a>0$), use the vertex formula:
$$x = -\frac{b}{2a}$$
3. Here, $a = 1$, $b = -4$, so
$$x = -\frac{-4}{2 \times 1} = \frac{4}{2} = 2$$
4. Find $f(2)$:
$$f(2) = 2^2 - 4 \times 2 + 9 = 4 - 8 + 9 = 5$$
5. The minimum point is at $(2, 5)$.
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6. **Sketch the graph of** $f(x) = x^2 - 4x + 9$.
7. Find the y-intercept by setting $x = 0$:
$$f(0) = 0^2 - 4 \times 0 + 9 = 9$$
So, the graph crosses the y-axis at $(0, 9)$.
8. Find the x-intercepts by solving $x^2 - 4x + 9 = 0$:
The discriminant is $\Delta = (-4)^2 - 4 \times 1 \times 9 = 16 - 36 = -20 < 0$, so no real roots.
Therefore, no x-intercepts.
9. The line of symmetry is the vertical line through the vertex:
$$x = 2$$
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10. **Find points of intersection between**
$$y = x^2 - 4x + 2$$
and
$$y = -x^2 - 8x$$
11. Set the two expressions equal:
$$x^2 - 4x + 2 = -x^2 - 8x$$
12. Bring all terms to one side:
$$x^2 - 4x + 2 + x^2 + 8x = 0 \\ 2x^2 + 4x + 2 = 0$$
13. Divide through by 2:
$$x^2 + 2x + 1 = 0$$
14. This factors as
$$(x + 1)^2 = 0$$
15. So, $x = -1$ is the single solution.
16. Find corresponding $y$:
$$y = (-1)^2 - 4(-1) + 2 = 1 + 4 + 2 = 7$$
17. The two graphs intersect at the point $(-1, 7)$.
Quadratic Minimum Intersection
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