1. **Problem statement:** We are given three functions:
- $f(x) = x^4 + x + 2$
- $g(x) = \frac{1}{3x + 1}$
- $h(x) = \frac{1}{\sqrt[3]{x - 2}}$
We need to find the domains of $f$, $g$, and $h$, then find the intersections of these domains:
- $\text{Dom}_f \cap \text{Dom}_g$
- $\text{Dom}_f \cap \text{Dom}_h$
- $\text{Dom}_g \cap \text{Dom}_h$
2. **Finding $\text{Dom}_f$:**
The function $f(x) = x^4 + x + 2$ is a polynomial, and polynomials are defined for all real numbers.
Therefore,
$$\text{Dom}_f = \mathbb{R}$$
3. **Finding $\text{Dom}_g$:**
The function $g(x) = \frac{1}{3x + 1}$ is defined for all real numbers except where the denominator is zero.
Set denominator equal to zero:
$$3x + 1 = 0$$
Solve for $x$:
$$3x = -1$$
$$x = \cancel{\frac{-1}{3}}$$
So $x = -\frac{1}{3}$ is excluded.
Therefore,
$$\text{Dom}_g = \mathbb{R} \setminus \left\{-\frac{1}{3}\right\}$$
4. **Finding $\text{Dom}_h$:**
The function $h(x) = \frac{1}{\sqrt[3]{x - 2}}$ involves the cube root in the denominator.
Cube root $\sqrt[3]{x - 2}$ is defined for all real $x$, but since it is in the denominator, it cannot be zero.
Set denominator equal to zero:
$$\sqrt[3]{x - 2} = 0$$
Cube both sides:
$$x - 2 = 0$$
$$x = \cancel{2}$$
So $x = 2$ is excluded.
Therefore,
$$\text{Dom}_h = \mathbb{R} \setminus \{2\}$$
5. **Find $\text{Dom}_f \cap \text{Dom}_g$:**
Since $\text{Dom}_f = \mathbb{R}$ and $\text{Dom}_g = \mathbb{R} \setminus \left\{-\frac{1}{3}\right\}$,
$$\text{Dom}_f \cap \text{Dom}_g = \mathbb{R} \setminus \left\{-\frac{1}{3}\right\}$$
6. **Find $\text{Dom}_f \cap \text{Dom}_h$:**
Since $\text{Dom}_f = \mathbb{R}$ and $\text{Dom}_h = \mathbb{R} \setminus \{2\}$,
$$\text{Dom}_f \cap \text{Dom}_h = \mathbb{R} \setminus \{2\}$$
7. **Find $\text{Dom}_g \cap \text{Dom}_h$:**
$$\text{Dom}_g = \mathbb{R} \setminus \left\{-\frac{1}{3}\right\}$$
$$\text{Dom}_h = \mathbb{R} \setminus \{2\}$$
Their intersection excludes both points:
$$\text{Dom}_g \cap \text{Dom}_h = \mathbb{R} \setminus \left\{-\frac{1}{3}, 2\right\}$$
**Final answers:**
- $\text{Dom}_f = \mathbb{R}$
- $\text{Dom}_g = \mathbb{R} \setminus \left\{-\frac{1}{3}\right\}$
- $\text{Dom}_h = \mathbb{R} \setminus \{2\}$
- $\text{Dom}_f \cap \text{Dom}_g = \mathbb{R} \setminus \left\{-\frac{1}{3}\right\}$
- $\text{Dom}_f \cap \text{Dom}_h = \mathbb{R} \setminus \{2\}$
- $\text{Dom}_g \cap \text{Dom}_h = \mathbb{R} \setminus \left\{-\frac{1}{3}, 2\right\}$
Function Domains 66A170
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