Eric’s statement is correct that the slopes of the perpendicular lines are opposites reciprocal with each other compared to Aviva’s. Aviva’s statement is correct but is not usually the case. An example is that when you are given these functions such as y = -2x + 3 and y = 1/2x + 4. The coefficients of the x variable are 2 and negative 1/2. The slopes must be in opposite signs so that the two functions will intersect at a common point and will form a ninety degree angle. This is the very basis of a perpendicular line because if both lines have the same slopes, then both lines are just parallel with each other, they cannot intersect.