1. The problem is to understand the vertex form of a quadratic function, which is given by the formula:
$$y = a(x - h)^2 + k$$
2. In this formula, $a$ controls the width and direction of the parabola (if $a > 0$, it opens upwards; if $a < 0$, it opens downwards).
3. The point $(h, k)$ is the vertex of the parabola, which is the highest or lowest point depending on the sign of $a$.
4. This form is useful because it directly shows the vertex and makes graphing easier.
5. For example, if $a = 2$, $h = 3$, and $k = -1$, the function is:
$$y = 2(x - 3)^2 - 1$$
6. This parabola opens upwards (since $a=2 > 0$), has its vertex at $(3, -1)$, and is narrower than the standard parabola $y = x^2$ because $|a| > 1$.
7. To find the y-intercept, set $x=0$:
$$y = 2(0 - 3)^2 - 1 = 2(9) - 1 = 18 - 1 = 17$$
So the y-intercept is at $(0, 17)$.
8. To find the x-intercepts, set $y=0$ and solve:
$$0 = 2(x - 3)^2 - 1$$
$$2(x - 3)^2 = 1$$
$$\cancel{2}(x - 3)^2 = \cancel{1} \frac{1}{2}$$
$$ (x - 3)^2 = \frac{1}{2}$$
$$x - 3 = \pm \sqrt{\frac{1}{2}} = \pm \frac{\sqrt{2}}{2}$$
$$x = 3 \pm \frac{\sqrt{2}}{2}$$
So the x-intercepts are at $\left(3 + \frac{\sqrt{2}}{2}, 0\right)$ and $\left(3 - \frac{\sqrt{2}}{2}, 0\right)$.
This completes the explanation of the vertex form and how to analyze the quadratic function.
Vertex Form 36Fd01
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