Quadratic Analysis 24Aa14
1. **State the problem:** Find the vertex and intercepts of the quadratic function $y = x^2 - 8x + 7$.
2. **Formula and rules:** The vertex of a parabola $y = ax^2 + bx + c$ is at $x = -\frac{b}{2a}$. The y-intercept is at $x=0$, and x-intercepts are found by solving $y=0$.
3. **Find the vertex:** Here, $a=1$, $b=-8$, $c=7$.
Calculate $x$-coordinate of vertex:
$$x = -\frac{-8}{2 \times 1} = \frac{8}{2} = 4$$
Calculate $y$-coordinate:
$$y = 4^2 - 8 \times 4 + 7 = 16 - 32 + 7 = -9$$
Vertex is at $(4, -9)$.
4. **Find y-intercept:** Substitute $x=0$:
$$y = 0^2 - 8 \times 0 + 7 = 7$$
Y-intercept is $(0,7)$.
5. **Find x-intercepts:** Solve $x^2 - 8x + 7 = 0$.
Calculate discriminant:
$$\Delta = (-8)^2 - 4 \times 1 \times 7 = 64 - 28 = 36$$
Since $\Delta > 0$, two real roots exist:
$$x = \frac{8 \pm \sqrt{36}}{2} = \frac{8 \pm 6}{2}$$
Roots:
$$x_1 = \frac{8 + 6}{2} = 7$$
$$x_2 = \frac{8 - 6}{2} = 1$$
X-intercepts are $(7,0)$ and $(1,0)$.
**Final answer:**
- Vertex: $(4, -9)$
- Y-intercept: $(0,7)$
- X-intercepts: $(1,0)$ and $(7,0)$