How do you find slope of the line perpendicular to the line y= -1? Algebra Forms of Linear Equations Equations of Perpendicular Lines 1 Answer smendyka Mar 17, 2017 The equation #y = -1# represents a horizontal line. A line perpendicular to #y = -1# will be a horizontal line. A horizontal line by definition has an undefined slope. Answer link Related questions How do you determine the equation of a line that is perpendicular to another? What is the relationship between equations of perpendicular lines? How do you determine if a line is perpendicular, parallel, or neither? How do you find the equation of the line perpendicular to the line #y=5# and passing through #(5, 4)#? What is the slope that is perpendicular to #2x+8y=9#? How do you determine if the two lines are parallel, perpendicular, or neither if line a passes... How do you find the equation of a line that is perpendicular to #y=2/3x-4# and goes through point (6,-2)? How do you determine if #5y+3x=1 # is parallel, perpendicular to neither to the line #y+10x=-3#? Question #3177e How do you find the equation of the line through the point (-4 , 5) and is perpendicular to the x axis? See all questions in Equations of Perpendicular Lines Impact of this question 1232 views around the world You can reuse this answer Creative Commons License