3.5 Slopes of Parallel and Perpendicular Lines
SlopeIntercept Form Review
• Slope• Rate of change (per)• Coefficient
• yintercept• Initial value• Constant term
Step 1: Find the slope
Step 2: Use the slope and a single point to find the yintercept.
Step 3: Plug the slope and yintercept into the equation .
Example 1: With help
Find an equation of the line that has a slope of and passes through the point (5,2).
Example 2: On your own
Find the equation of the line in slopeintercept form that passes through the points P(7,2) and R(1,4).
Step 1: Find the slope How?– You are given the slope!
– Find the slope using 2 points and the slope formula (rise/run)
– Compare the slope to another line (What does this mean?!?)
Step 2: Use the slope and a single point to find the yintercept.
Step 3: Plug the slope and yintercept into the equation.
Writing the equation of a line in slopeintercept form
Parallel lines have the same slope, but usually different yintercepts.
• Examples of parallel lines
Parallel Lines
Both have slope of 4Both have slope of 2/3
Both have an undefined slope (vertical)
3.5 Slopes of Parallel and Perpendicular Lines
Perpendicular lines have the slopes that are opposite reciprocals
> Opposite = different signs> Reciprocals = numerator and denominator are flipped
• Examples of perpendicular lines
Perpendicular Lines
Slopes are opposite reciprocals
Perpendicular with one vertical and one horizontal line.
Slopes are opposite reciprocals
Homework • 3.5 p.160 #712,1420 Evens (Day 1)
