The slope of AB = 1/2
The slope of ED = -2
1/2 and -2 are negative reciprocals of each other. This is the definition of perpendicular lines. Hence,
AB and ED are perpendicular.
The slope is also known as rise/run.
We take any point on a graph and move along the line to another point. The amount we moved in y direction divided by the amount moved in x direction is the slope.