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)