Answer:
Slope of AB is undefined; slope of CD is 0; the lines are perpendicular.
Step-by-step explanation:
Slope (M) can be found with the equation M=y2-y1/x2-x1, or change in y over change in x. In this equation, finding the slope is very easily done without even using the equation, because it can be seen in AB that the x value doesn't change (showing a vertical line), and in CD the y value doesn't change (showing a horizontal value). When they intercept, they make a cross-shape, so they are perpendicular.