Mathematics
problems often deal with parallel and perpendicular lines.
Since these are such popular lines, it is important that we remember
some information about their slopes.
Parallel
Lines: (same
slope!)
Parallel
lines are marked with "feathers" to show that they are parallel.
These "feathers" look like "greater than" symbols.
Parallel
lines have the same slope.
The symbol to indicate parallel lines is two vertical
bars.
It looks something like the number 11.
where l_{1} and l_{2 }are lines
m_{1} and m_{2} are slopes
y = 3x
+ 5
y = 3x  7
y = 3x + 0.5
y = 3x 
These
lines are ALL parallel.
They all have the same slope (m).
(Remember y = mx +
b.) 

Example:
The slope of
is
and
.
Find the slope of
.
Since the lines are parallel, the slopes are the same.
The slope of
is
also
. ANSWER 
Perpendicular
Lines:
(negative reciprocal slopes!)
Perpendicular
lines have negative reciprocal slopes.
The symbol to
indicate perpendicular is an upsidedown capital T.
where l_{1} and l_{2 }are lines
m_{1} and m_{2} are slopes
To find a
negative reciprocal of a number, flip the number over (invert) and
negate that value.


These
lines are perpendicular.
Their slopes (m) are negative
reciprocals.
(Remember y = mx +
b.) 

Example:
The slope of
is
and
.
Find the slope of
.
Since the lines are perpendicular, the slopes are negative
reciprocals.
The slope of
is
.
ANSWER 
