There are basically three types of line equations:

1. y=mx+b

x and y represent a point on the line (x,y) m represents the slope of the line b represents the y-intercept to find the y-intercept let x=0 to find the x-intercept let y=0

2. ax+by=c

x and y represent a point on the line (x,y) -a/b represents the slope of the line a, b, and c are constants the y-intercept is c/b when x=0 the x-intercept is c/a when y=0

3. (y-y1)=m(x-x1)

x1 and y1 represent a point(x1,y1) on the line m represents the slope of the line *usually the preferred formula for lines because if you know a point on the line and the slope you know the equation

Parallel lines have the same slope

Perpedicular lines have slopes that are negative reciprocals e.g. if m is the slope of one line then the slope of the other line is -1/m

Slope can be calculated by using this formula: (y2-y1)/(x2-x1) *or is more easily known as rise/run