In order to find the equation of the line that passes through the points (2,-1) and (8,1), you must find the slope.
y₁ ⇒ -1
y₂ ⇒ 1
x₂ ⇒8
x₁ ⇒ 2
Slope Formula: y₂ - y₁ 1 + 1 2 1
------------- = ----------- = ------- = ------
x₂ - x₁ 8 - 2 6 3
Slope Intercept Form: y = mx + b
m = slope
b = y - intercept
y = 1/3x is your final equation in slope intercept form.
