Question: Write a slope-intercept equation for a line passing through the point $(4, -2)$ that is parallel to the line $4x + 7y = 9$. Then write a second equation for a line passing through the point $(4, -2)$ that is perpendicular to the line $4x + 7y = 9$.
1. **State the problem:**
We need to find two equations of lines passing through the point $(4, -2)$: one parallel and one perpendicular to the line $4x + 7y = 9$.
2. **Find the slope of the given line:**
Rewrite $4x + 7y = 9$ in slope-intercept form $y = mx + b$.
$$7y = -4x + 9$$
$$y = \frac{-4}{7}x + \frac{9}{7}$$
So, the slope of the given line is $m = -\frac{4}{7}$.
3. **Equation of the parallel line:**
Parallel lines have the same slope. So the slope of the parallel line is also $m = -\frac{4}{7}$.
Use point-slope form:
$$y - y_1 = m(x - x_1)$$
where $(x_1, y_1) = (4, -2)$.
$$y - (-2) = -\frac{4}{7}(x - 4)$$
$$y + 2 = -\frac{4}{7}x + \frac{16}{7}$$
Subtract 2 from both sides:
$$y = -\frac{4}{7}x + \frac{16}{7} - 2$$
Convert 2 to fraction with denominator 7:
$$2 = \frac{14}{7}$$
So,
$$y = -\frac{4}{7}x + \frac{16}{7} - \frac{14}{7} = -\frac{4}{7}x + \frac{2}{7}$$
4. **Equation of the perpendicular line:**
The slope of a line perpendicular to slope $m$ is the negative reciprocal:
$$m_{\perp} = -\frac{1}{m} = -\frac{1}{-\frac{4}{7}} = \frac{7}{4}$$
Use point-slope form again:
$$y - (-2) = \frac{7}{4}(x - 4)$$
$$y + 2 = \frac{7}{4}x - 7$$
Subtract 2 from both sides:
$$y = \frac{7}{4}x - 7 - 2$$
$$y = \frac{7}{4}x - 9$$
**Final answers:**
- Parallel line: $$y = -\frac{4}{7}x + \frac{2}{7}$$
- Perpendicular line: $$y = \frac{7}{4}x - 9$$