The distance d between any two points and in a plane is given by the distance formula: Example 1 Find the distance between (2,-7) and (-1,-3). The coordinates of the midpoint m between any two points are given by the mid point formula: Example 2 Find the midpoint of a line segment between (2,-5) and (7,-1). The slope of a line measures the steepness of the line. The slope also indicates whether as values of x increases, a line is rising (positive slope), falling (negative slope) or constant (slope of 0). Slope of a Line The slope of a line through two points is All lines except vertical lines have a slope. The slope of a vertical line is undefined and the slope of a horizontal line is 0. Example 3 Slope of a line joining (2,-5) and (-2,1) If we start at (-2,1) If two lines are parallel, they have the same inclination, so parallel lines have the same slope. If two lines are perpendicular, they intersect at a
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