1.3 Linear Equations in Two Variables

PHSP Pre-Calc

Slope =

mx or rise/run

intercept =

+ b , (0,b)

Point-intercept form formula

y = mx + b

A vertical line has an equation of the form

x = a , slope is undefined

When m = 0, the line is…

horizontal

Finding slope (m)

= Change in y/change in x = rise/run = y₂-y₁/x₂-x₁

point-slope form (two-point form)

is useful for finding the equation of a line. We know the slope (m=a) and a point (x,y)

point-slope form formula

y-y₁ = m(x-x₁)

Parallel lines

Two distinct nonvertical lines and their slopes are equal: m₁ = m₂

perpendicular

Two nonvertical lines and their slopes are negative: m₁ = -1/m₂ (negative reciprocal)