## Introductory Algebra for College Students (7th Edition)

m=$\frac{y_2-y_1}{x_2-x_1}$ m=$\frac{-1-(-1)}{3-4}$ m=$\frac{-1+1}{-1}$ m=$\frac{0}{-1}$ m=0 The slope is zero, therefore the line is horizontal.