1. Geometry Review on Algebra 1
Equations of Lines
Geometry Review on Algebra 1

2. y = mx + b Slope Intercept form
Y intercept is where the line intersects the y-axis.
Lower case b is the symbol for y-intercept.
Lower case m is the symbol for slope.

3. Point SLOPE Form

4. Vertical and Horizontal
X= # equations have no slope and are always vertical lines.
Y= # equations have zero slope and are always horizontal lines.

5. Parallel
Equations of parallel lines MUST have the same slope and MUST have different y-intercepts.

6. Perpendicular
Perpendicular lines MUST have opposite reciprocal slopes.
Opposite reciprocal means that the fraction of slope must be flipped and opposite signs.
Examples: is perpendicular to −1 1
5 2 is perpendicular to −2 5
−4 7 is perpendicular to 7 3

7. 2 points
When writing an equation of a line given only two points you must follow the following procedure:
Calculate the slope between the two points.
Substitute one of the points and your slope into the POINT SLOPE EQUATION.