Question: Write the following as a single rational expression.
$\frac{1}{x^3} \div \frac{2}{x}$
1. **State the problem:**
Write the expression $\frac{1}{x^3} \div \frac{2}{x}$ as a single rational expression.
2. **Recall the division rule for fractions:**
Dividing by a fraction is the same as multiplying by its reciprocal. So,
$$\frac{a}{b} \div \frac{c}{d} = \frac{a}{b} \times \frac{d}{c}$$
3. **Apply the rule:**
$$\frac{1}{x^3} \div \frac{2}{x} = \frac{1}{x^3} \times \frac{x}{2}$$
4. **Multiply the numerators and denominators:**
$$= \frac{1 \times x}{x^3 \times 2} = \frac{x}{2x^3}$$
5. **Simplify the expression:**
Cancel common factors using the property $\frac{x}{x^3} = \frac{\cancel{x}^1}{\cancel{x}^3} = \frac{1}{x^{3-1}} = \frac{1}{x^2}$:
$$\frac{x}{2x^3} = \frac{\cancel{x}^1}{2 \times \cancel{x}^3} = \frac{1}{2x^2}$$
6. **Final answer:**
$$\boxed{\frac{1}{2x^2}}$$