Sample Response: The lines are perpendicular because perpendicular lines have slopes that are opposite reciprocals. To compare the slopes, you can rewrite the second equation in slope-intercept form as y = (–1/3)x + 1. The slope of the given line is 3, and the slope of the second line is –1/3. These have a product of –1, which means they are opposite reciprocals. Thus, the two lines are perpendicular. What did you include in your response? Check all that apply. The lines are perpendicular. Perpendicular lines have opposite reciprocal slopes. Opposite reciprocals have a product of –1. The given line has a slope of 3, and the second line has a slope of –1/3.