Find the slope of the given line
Take the negative reciprocal of that slope
Use that slope for the perpendicular line
If a point is given, use point-slope form: y – y1 = m(x – x1)
If the line is in standard form, rewrite it in slope-intercept form first if needed
Check that the product of the two slopes is -1
For vertical lines, the perpendicular line is horizontal
For horizontal lines, the perpendicular line is vertical