What's the slope of y=-1? Algebra Graphs of Linear Equations and Functions Horizontal and Vertical Line Graphs 1 Answer F. Javier B. May 17, 2018 #0#. See explanation below Explanation: We define slope as #m=(y_1-y_0)/(x_1-x_0)# In a constant function as given #y=-1# we have #y_1=y_0=-1# And then #m=(-1-(-1))/(x_1-x_0)=0/(x_1-x_0)=0# Answer link Related questions What are horizontal or vertical line graphs? What would the #(x,y)# table look like for a horizontal and a vertical line graph? How do you graph #y=4#? What are some examples of when you would see horizontal or vertical line graphs? How do you graph #x=-1#? What is the equation for the x-axis? What is the equation for the y-axis? How do you graph #y=1/2#? How do you graph #x=100#? In which quadrant do the lines #x=3# and #y=-4# intersect? See all questions in Horizontal and Vertical Line Graphs Impact of this question 19455 views around the world You can reuse this answer Creative Commons License