△ABC has vertices at A(-2, 4), B(-1, 1), and C(2, 2). The slope of AB¯¯¯¯¯¯¯¯ is , the slope of BC¯¯¯¯¯¯¯¯ is , and the slope of AC¯¯¯¯¯¯¯¯ is . △ABC a right triangle because