1. **State the problem:**
We are given a piecewise function:
$$f(x) = \begin{cases} -\frac{1}{3}(x + 4)^2 + 3 & x \leq -1 \\ 3|x - 2| - 4 & -1 < x < 4 \\ (x - 6)^3 + 3 & x \geq 4 \end{cases}$$
We need to:
A. Find the domain and range.
B. Identify discontinuities and classify their types.
2. **Domain:**
The domain is all $x$ values for which $f(x)$ is defined.
Each piece covers:
- $x \leq -1$
- $-1 < x < 4$
- $x \geq 4$
Together, these cover all real numbers, so:
$$\text{Domain} = (-\infty, \infty)$$
3. **Range:**
Analyze each piece:
- For $x \leq -1$, $f(x) = -\frac{1}{3}(x + 4)^2 + 3$ is a downward parabola with vertex at $x = -4$:
$$f(-4) = -\frac{1}{3}(0)^2 + 3 = 3$$
As $x$ moves away from $-4$, $(x+4)^2$ increases, so $f(x)$ decreases without bound.
So range for this piece is $(-\infty, 3]$.
- For $-1 < x < 4$, $f(x) = 3|x - 2| - 4$.
The absolute value has a minimum at $x=2$:
$$f(2) = 3|0| - 4 = -4$$
At the endpoints:
$$f(-1) = 3| -1 - 2| - 4 = 3 \times 3 - 4 = 5$$
$$f(4) = 3|4 - 2| - 4 = 3 \times 2 - 4 = 2$$
Since $x$ is strictly between $-1$ and $4$, these endpoint values are not included.
Range for this piece is $(-4, 5)$.
- For $x \geq 4$, $f(x) = (x - 6)^3 + 3$ is a cubic function.
At $x=4$:
$$f(4) = (4 - 6)^3 + 3 = (-2)^3 + 3 = -8 + 3 = -5$$
As $x \to \infty$, $f(x) \to \infty$.
So range for this piece is $[-5, \infty)$.
4. **Combine ranges:**
Piece 1: $(-\infty, 3]$
Piece 2: $(-4, 5)$
Piece 3: $[-5, \infty)$
Check overlaps:
- Piece 1 and 2 overlap between $(-4, 3]$.
- Piece 2 and 3 overlap between $[-5, 5)$ and $[-5, \infty)$, but note piece 3 starts at $-5$.
Overall range is:
$$(-\infty, 5) \cup [-5, \infty) = (-\infty, \infty)$$
Because piece 3 covers from $-5$ to infinity and piece 1 covers down to $-\infty$, the entire real line is covered.
5. **Discontinuities:**
Check at boundaries $x = -1$ and $x = 4$.
- At $x = -1$:
Left limit:
$$f(-1^-) = -\frac{1}{3}(-1 + 4)^2 + 3 = -\frac{1}{3}(3)^2 + 3 = -3 + 3 = 0$$
Right limit:
$$f(-1^+) = 3| -1 - 2| - 4 = 3 \times 3 - 4 = 5$$
Since left and right limits differ, there is a jump discontinuity at $x = -1$.
- At $x = 4$:
Left limit:
$$f(4^-) = 3|4 - 2| - 4 = 3 \times 2 - 4 = 2$$
Right limit:
$$f(4^+) = (4 - 6)^3 + 3 = -8 + 3 = -5$$
Left and right limits differ, so jump discontinuity at $x = 4$.
6. **Summary:**
- Domain: $(-\infty, \infty)$
- Range: $(-\infty, \infty)$
- Discontinuities: jump discontinuities at $x = -1$ and $x = 4$.
Piecewise Function 2009F9
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