Quadratic Expression 9D556C
1. **State the problem:** Simplify and analyze the quadratic expression $-3x^2 + 12x$.
2. **Formula and rules:** This is a quadratic expression of the form $ax^2 + bx + c$ where $a = -3$, $b = 12$, and $c = 0$.
3. **Factor the expression:** Factor out the greatest common factor (GCF) which is $-3x$:
$$-3x^2 + 12x = -3x(x - 4)$$
4. **Find the roots (zeros):** Set the expression equal to zero:
$$-3x(x - 4) = 0$$
This implies either $-3x = 0$ or $x - 4 = 0$, so
$$x = 0 \quad \text{or} \quad x = 4$$
5. **Vertex and axis of symmetry:** The vertex of a parabola $y = ax^2 + bx + c$ is at
$$x = -\frac{b}{2a} = -\frac{12}{2 \times (-3)} = 2$$
Calculate $y$ at $x=2$:
$$y = -3(2)^2 + 12(2) = -3(4) + 24 = -12 + 24 = 12$$
So the vertex is at $(2, 12)$.
6. **Interpretation:** The parabola opens downward (since $a = -3 < 0$), has roots at $0$ and $4$, and a maximum point at $(2, 12)$.
**Final answer:**
$$-3x^2 + 12x = -3x(x - 4)$$
Roots: $x=0$, $x=4$
Vertex: $(2, 12)$
Parabola opens downward.