Inverse Proportionality D73E18
1. **Problem Statement:**
We are given that $y$ is inversely proportional to $x$, and when $x=2$, $y=\frac{1}{2}$. We need to find the graph that represents this relationship and then find $y$ when $x=4$.
2. **Formula and Explanation:**
If $y$ is inversely proportional to $x$, then:
$$y = \frac{k}{x}$$
where $k$ is a constant.
3. **Find the constant $k$:**
Given $x=2$ and $y=\frac{1}{2}$, substitute these values:
$$\frac{1}{2} = \frac{k}{2}$$
Multiply both sides by 2:
$$k = 1$$
4. **Equation of the relationship:**
$$y = \frac{1}{x}$$
5. **Graph selection:**
The graph of $y=\frac{1}{x}$ is a hyperbola that decreases as $x$ increases, approaching zero but never touching the axes. Among the given graphs, the one that shows this behavior with $k=1$ is the green curve (Graph A) starting near $y=4$ at $x=0$ and decreasing smoothly.
6. **Find $y$ when $x=4$:**
Substitute $x=4$ into the equation:
$$y = \frac{1}{4}$$
**Final answers:**
- a) The graph that shows this relationship is Graph A (green curve).
- b) When $x=4$, $y=\frac{1}{4}$.