Two lines are perpendicular when... the product of their slope is -1, the product of the slope is greater than 0, they have the same slope, or when the slope is undefined?

The answer is the product of their slope is -1.

First, let's break this down. Perpendicular lines are line with opposite reciprocal slopes. Opposite meaning the inverse sign and reciprocal meaning flipped.

For instance,

If a line had the slope of 5, its inverse would have a slope of -1/5.

Now, if we multiply these numbers together,

5 * -1/5 = -1

The 5's cancel out.

This works for any two perpendicular lines

a function could be identified in 3 ways either on a chart,graph, or ordered pairs. first a function is that each point has its own. the rule is that there can be many x's to one y but there can not be 2 x's at different y's. so on a graph when you put a straight line through the y's there should be one dot only to be a function.

step-by-step explanation: