K 1 represents the slope of a straight line, and k2 represents the slope of another straight line. K 1*k2=- 1 indicates that two straight lines are perpendicular. In rectangular coordinate system, straight junior high school is generally set to y=kx+b, where k is the slope. Example: Find the straight line passing through (1, 0) and (4, 3), subtract 3 -0=3 from the ordinate of two points, and then divide by the abscissa and subtract 4- 1=3 to get the slope.