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

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.

Point SLOPE Form

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

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

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

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.