Finding the Equation of a Line

Method 1 (slope-intercept form): y = mx + b

EX: Find an equation of a line through (2,4) & (6,-2).

Slope: -6/4 or – 3/2 or -1.5 (easy - use the slope formula)

y-intercept: y = m ∙ x + b

4 = -1.5 ∙ 2 + b (plug values for y,m, & x - we could also have substituted 6 for x & -2 for y)

7 = b

Equation: y = -1.5x + 7

Method 2 (point-slope form): y – y₀ = m(x – x₀)

EX: Find an equation of a line through (-3,4) & (6,-1).

Slope: -5/9 (easy - use the slope formula)

Equation: y - 4 = -5/9(x + 3) (plug values for y_o, m, & x_o - we could also have substituted 6 for x & -1 for y)