Question: Find the equation of the line that is perpendicular to $y = -\frac{2}{3} x$ and contains the point $(4,-8)$. $y = \frac{3}{2} x + ?$
1. **State the problem:** Find the equation of the line perpendicular to $y = -\frac{2}{3} x$ that passes through the point $(4,-8)$.
2. **Recall the slope of the given line:** The given line is $y = -\frac{2}{3} x$, so its slope is $m_1 = -\frac{2}{3}$.
3. **Find the slope of the perpendicular line:** The slope of a line perpendicular to another is the negative reciprocal of the original slope.
$$m_2 = -\frac{1}{m_1} = -\frac{1}{-\frac{2}{3}} = \frac{3}{2}$$
4. **Use the point-slope form:** The equation of a line with slope $m$ passing through point $(x_1,y_1)$ is
$$y - y_1 = m(x - x_1)$$
Substitute $m = \frac{3}{2}$ and point $(4,-8)$:
$$y - (-8) = \frac{3}{2}(x - 4)$$
5. **Simplify the equation:**
$$y + 8 = \frac{3}{2}x - \frac{3}{2} \times 4$$
$$y + 8 = \frac{3}{2}x - 6$$
6. **Isolate $y$ to get slope-intercept form:**
$$y = \frac{3}{2}x - 6 - 8$$
$$y = \frac{3}{2}x - 14$$
7. **Final answer:** The equation of the line perpendicular to $y = -\frac{2}{3} x$ and passing through $(4,-8)$ is
$$y = \frac{3}{2}x - 14$$