Slope of AB m = (y2 - y1)/(x2 - x1) m = (11 - (-4))/(2 - (-1)) m = (11 + 4)/(2 + 1) m = 15/3 m = 5 The slope of line AB is 5
Slope of CD m = (y2 - y1)/(x2 - x1) m = (10 - 1)/(4 - 1) m = 9/3 m = 3 The slope of CD is 3
Since the two slopes are not equal, this means the lines are not parallel. Since (slope of AB)*(slope of CD) = 5*3 = 15 is not equal to -1, this means the lines are not perpendicular
