请给我讲讲这道题---**【题目】** 如图，一次函数 $y = x + 4$ 的图像交 $x$ 轴于点 $A$，交反比例函数 $y = \frac{k}{x} (k \neq 0, x < 0)$ 的图像于点 $B(-1, a)$，将一次函数 $y = x + 4$ 的图像向下平移 $m (m > 0)$ 个单位长度，所得的图像交 $x$ 轴于点 $C$。 **(1) 求反比例函数 $y = \frac{k}{x}$ 的表达式；** **(2) 当 $\triangle ABC$ 的面积为3时，求 $m$ 的值。** --- **Chart/Diagram Description:** * **Type:** Coordinate Plane with Graphs of Functions. * **Main Elements:** * **Coordinate Axes:** A horizontal X-axis and a vertical Y-axis, intersecting at the origin O. Arrows indicate positive directions. * **Graphs of Functions:** * One straight line representing the linear function $y = x + 4$. It intersects the X-axis at point A. * A curve in the second quadrant, representing the inverse proportion function $y = \frac{k}{x}$ (for $x < 0$). * The straight line $y = x + 4$ and the curve $y = \frac{k}{x}$ intersect at point B. * Another straight line, parallel to $y = x + 4$ and located below it, representing the translated linear function. This translated line intersects the X-axis at point C. * **Points:** * **O:** Origin (0,0). * **A:** Intersection point of the line $y = x + 4$ with the X-axis. Located on the negative X-axis. * **B:** Intersection point of the line $y = x + 4$ and the curve $y = \frac{k}{x}$. Located in the second quadrant. Its coordinates are given as $(-1, a)$. * **C:** Intersection point of the translated line with the X-axis. Located on the negative X-axis, to the right of A but to the left of O. * **Relative Position:** Point A, C, O are collinear on the X-axis, with A being furthest left, then C, then O. Point B is above the X-axis. The translated line is below the original line.