# Parallel/Perpendicular Lines

• Dec 16th 2008, 09:28 AM
kiwifruit
Parallel/Perpendicular Lines
So here's the problem: passes through (-2,2), parallel to graph of -2x + y = 4. Then I graph the line that satisfies the condition, but what I really need to know is just how to figure out the slope.
• Dec 16th 2008, 09:41 AM
Plato
Quote:

Originally Posted by kiwifruit
So here's the problem: passes through (-2,2), parallel to graph of -2x + y = 4. Then I graph the line that satisfies the condition, but what I really need to know is just how to figure out the slope.

Parallel have the same slope.
So any line parallel to -2x + y = 4 looks like -2x + y = K.
Just substitute the values for x & y to find K.
• Dec 16th 2008, 09:45 AM
Chris L T521
Quote:

Originally Posted by kiwifruit
So here's the problem: passes through (-2,2), parallel to graph of -2x + y = 4. Then I graph the line that satisfies the condition, but what I really need to know is just how to figure out the slope.
When lines are parallel, they have the same slope. [i.e. if the slope of one line is $m=a$ then line two has a slope of $m_{\parallel}=a$
When lines are perpendicular, its a little different. If line one has a slope of $m=a$, then line two has a slope of $m_{\bot}=-\frac{1}{a}$