
General Form of equation of a line
Ax+By=C

Slope (steepness) Formula
 m= y2y1
 x2x1
 m= rise = vertical change
 run horizontal change

How do you read the graph?
Left to right


Falling
m<0 negative, hence y=b

Horizontal
zero (m=0) hence y=b

Vertical
Undefined, hence x=a

Slope intercept form equation
y=mx+b
slope = m
coordinate y= b

How do we write the equation for slope intercept form?
Isolate y variable so that it is
y= slope (x) + b from given equation

What is the yintercept always equivalent to?
the y coordinate

Point slope formula
Used if you have only one point and the slope
yy1=m(xx1)
(does not work for verticle lines)

How do you find the equation of a line given 2 points?
Use the points to find the slope, and then plug it into the pointslope formula

How do you tell if lines are parallel
They must have the same slope
m1=m2

How do you find the equation of a parallel line?
 1) write slope intercept form
 2) identify the slope given (parallel lines have same slope)
 3) substitute slope into equation of the line
 4) substitute in variables (coordinates given)
 5) since b is the only variable left, SOLVE FOR B

What is unique ( and always true) about perpendicular slopes?
The slopes' of the two lines will always be negative reciprocals of eachother

Which two types of lines do not share the perpendicular slope property?
 horizontal, m=0
 vertical, slope undefined

How do you find the equation of a perpendicular line?
 1) Identify the slope of the given line
 2) identify its reciprocal to find the slope that is perpendicular to given line
 3) Write equation of the line we are looking for in slopeintercept form y=m2x+b
 4) substitute the reciprocal slope back into equarion
 5) plug in coordinates
 6) since b is the only variable left, SOLVE FOR B

