1. **State the problem:** Find the axis of symmetry, vertex, y-intercept, and x-intercepts of the parabola given by the equation $y = 3x^2 + 12x + 9$.
2. **Axis of symmetry formula:** For a quadratic $y = ax^2 + bx + c$, the axis of symmetry is given by
$$x = -\frac{b}{2a}$$
where $a = 3$ and $b = 12$.
3. **Calculate axis of symmetry:**
$$x = -\frac{12}{2 \times 3} = -\frac{12}{6} = -2$$
4. **Find the vertex:** The vertex lies on the axis of symmetry. Substitute $x = -2$ into the equation:
$$y = 3(-2)^2 + 12(-2) + 9 = 3(4) - 24 + 9 = 12 - 24 + 9 = -3$$
So, the vertex is at $(-2, -3)$.
5. **Find the y-intercept:** Set $x=0$:
$$y = 3(0)^2 + 12(0) + 9 = 9$$
So, the y-intercept is at $(0, 9)$.
6. **Find the x-intercepts:** Set $y=0$ and solve for $x$:
$$0 = 3x^2 + 12x + 9$$
Divide both sides by 3:
$$0 = \cancel{3}x^2 + \cancel{3}4x + \cancel{3}3 \Rightarrow 0 = x^2 + 4x + 3$$
Factor the quadratic:
$$0 = (x + 3)(x + 1)$$
Set each factor to zero:
$$x + 3 = 0 \Rightarrow x = -3$$
$$x + 1 = 0 \Rightarrow x = -1$$
7. **Write x-intercepts as coordinates:**
Left x-intercept: $(-3, 0)$
Right x-intercept: $(-1, 0)$
**Final answers:**
- Axis of symmetry: $x = -2$
- Vertex: $(-2, -3)$
- Y-intercept: $(0, 9)$
- Left x-intercept: $(-3, 0)$
- Right x-intercept: $(-1, 0)$
Parabola Properties Ad7456
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