Parallel & Perpendicular

Parallel & Perpendicular Graphs

Parallel lines run in the exact same direction, and never intersect.

…they have the same exact

SLOPE !!!

…we can tell if lines are parallel just by looking at their formulas!!

y = 5x + 4

y = 5x - 6

“Are these lines parallel?” Same slope!!! They are PARALLEL !!

Now, the opposite of parallel is PERPENDICULAR

PERPENDICULAR : two lines that run at a perfect right angle to each other

We can also tell when lines are perpendicular just by looking at the slopes…

y=½x+4

y = -2x + 19

…just multiply the SLOPES…..if the answer is -1, then the lines are PERPENDICULAR !!!

(½)(-2) = -1 They’re perpendicular!!

Even Easier! To get the perpendicular line slope, just find the “Opposite Reciprocal” of the original slope!

Opposite WHAT??

Reciprocal just means FLIP the FRACTION!!!

Original Slope 3/4

Perpendicular Slope: (Opposite Reciprocal) - 4/3

1/2

-2/1

-3

+1/3

Practice. Tell if each pair of lines are “Perpendicular”, “Parallel”, or “Neither”. y = 12x + 4 y = 12x – 6.4

y = (4/3)x - 8 y = (3/4)x + 6

y = -6x + 4 y = (1/6)x – 123

y = 3x y = 3x - 3124234