Slope of Horizontal Line
Zero
Slope of Vertical Line
Undefined
Equation of Vertical Line
x = a number (where it crosses x-axis)
Equation of Horizontal Line
y = a number (where it crosses y-axis)
Slope Intercept Form of Equation of Line
y = mx + b
Standard Form of Equation of Line
Ax + By = C
Point-Slope Form of Equation of LIne
y - y1 = m(x - x1)
Slope Formula
m = (y2 - y1) / (x2 - x1)
Letter that is slope
m
Letter that is y-intercept
b
y-intercept
Point where line crosses y-axis (put in zero for x): (0,b)
x-intercept
Point where line crosses x-axis (put in zero for y): (a,0)
Words in word problem that mean slope
Rate of Change
Direction of positive slope
Up to the right
Direction of negative slope
Down to the right
Slopes of parallel lines....
... are the same slope
Slopes of perpendicular lines...
... have opposite reciprocal slope (one is +, one is - AND they are reciprocals)