See attached graphs:
Work Step by Step
Graph the points for each problem and you will notice that the points form a type of line: a) The line is increasing, as the x- and y-values are directly proportional to each other. This means that the slope is positive. b) The line is decreasing, as the x- and y- values are inversely proportional to each other. This means that the slope is negative. c) The line is vertical which creates an undefined slope.