1. **State the problem:** We need to sketch the graph of the cubic function $$y = (x-3)(x+1)(x+4)$$.
2. **Formula and important rules:** This is a cubic polynomial in factored form. The roots (x-intercepts) are the values of $x$ that make each factor zero: $x=3$, $x=-1$, and $x=-4$.
3. **Find the roots:**
- Set each factor equal to zero:
$$x-3=0 \Rightarrow x=3$$
$$x+1=0 \Rightarrow x=-1$$
$$x+4=0 \Rightarrow x=-4$$
4. **Determine the end behavior:**
- The leading term of the expanded polynomial will be $x^3$ (since multiplying $x \cdot x \cdot x$).
- For large positive $x$, $y \to +\infty$.
- For large negative $x$, $y \to -\infty$.
5. **Find the y-intercept:**
- Set $x=0$:
$$y = (0-3)(0+1)(0+4) = (-3)(1)(4) = -12$$
6. **Sketch key points:**
- Roots at $x=-4, -1, 3$ (where $y=0$).
- Y-intercept at $(0, -12)$.
7. **Plot and connect:**
- The graph crosses the x-axis at the roots.
- Since all roots are simple (multiplicity 1), the graph crosses the x-axis at each root.
- The graph goes from $-\infty$ at left, crosses at $-4$, goes up and down crossing at $-1$, then crosses at $3$ and goes to $+\infty$.
**Final answer:** The graph of $$y = (x-3)(x+1)(x+4)$$ is a cubic curve with roots at $-4$, $-1$, and $3$, y-intercept at $-12$, and end behavior going down to the left and up to the right.
Cubic Polynomial 84B681
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