Math help

1. Sep 16, 2005

modeman

I heel help with my math, so if you could do the work for me, no just kidding! But seriously, I need help.

Find the slope of the line that passes through eash pair of points. Then determine whether the line rises to the right, falls to the right, is horizontal, or is vertical.

18. (6,1) (8,-4)

20. (-6,-5) (4,1)

22. (2.5,3) (1,-9)

Determine the value of r so that a line through the points with the given coordinates has the given slope.

36. Graph a line through (-4,1) that is perpendicular to a line whose slope is -3/2

38. Graph a line through the orgin that is parallel to the graph of x+y=10

40. One line has a slope of 0 and another has an undefined, but they both pass through (-3,-3). Graph the lines.

How do I do these? What are the formulas for these and what do the last three mean?

2. Sep 16, 2005

TD

The slope is given by the difference of the y-values divided by the difference of the x-values.

$$m = \frac{{y_2 - y_1 }} {{x_2 - x_1 }} = \frac{{\Delta y}} {{\Delta x}}$$

The equation of a line through a point $\left( {x_1 ,y_1 } \right)$ is given by $y - y_1 = m\left( {x - x_1 } \right)$.

Two slopes are perpendicular if $m_1 m_2 = - 1 \Leftrightarrow m_1 = - \frac{1}{{m_2 }}$

Two lines are parallel if their slopes are the same.

Try to understand what that last question means

3. Sep 16, 2005