Question: Find an equation for the line with the given properties: Perpendicular to the line $-7x-9y=-35$; containing the point $(-4,-7)$
1. **State the problem:** We need to find the equation of a line that is perpendicular to the line given by $$-7x - 9y = -35$$ and passes through the point $$(-4, -7)$$.
2. **Rewrite the given line in slope-intercept form:**
$$-7x - 9y = -35$$
Add $$7x$$ to both sides:
$$-9y = 7x - 35$$
Divide both sides by $$-9$$:
$$y = \frac{7x - 35}{-9} = -\frac{7}{9}x + \frac{35}{9}$$
3. **Identify the slope of the given line:**
The slope $$m_1$$ is $$-\frac{7}{9}$$.
4. **Find the slope of the perpendicular line:**
The slope $$m_2$$ of a line perpendicular to another with slope $$m_1$$ is the negative reciprocal:
$$m_2 = -\frac{1}{m_1} = -\frac{1}{-\frac{7}{9}} = \frac{9}{7}$$
5. **Use point-slope form to find the equation of the perpendicular line:**
Point-slope form is:
$$y - y_1 = m(x - x_1)$$
Using point $$(-4, -7)$$ and slope $$\frac{9}{7}$$:
$$y - (-7) = \frac{9}{7}(x - (-4))$$
Simplify:
$$y + 7 = \frac{9}{7}(x + 4)$$
6. **Expand and simplify:**
$$y + 7 = \frac{9}{7}x + \frac{36}{7}$$
Subtract 7 from both sides:
$$y = \frac{9}{7}x + \frac{36}{7} - 7$$
Convert 7 to $$\frac{49}{7}$$:
$$y = \frac{9}{7}x + \frac{36}{7} - \frac{49}{7} = \frac{9}{7}x - \frac{13}{7}$$
7. **Final equation:**
$$y = \frac{9}{7}x - \frac{13}{7}$$
This is the equation of the line perpendicular to $$-7x - 9y = -35$$ and passing through $$(-4, -7)$$.