Final answer:
The correct formula to calculate the slope (m) of a straight line using two points is a) m = (y2 - y1) / (x2 - x1), representing the rise over run between those points.
Step-by-step explanation:
To find the slope of a line using two points, you should use the formula m = (y2 - y1) / (x2 - x1), which calculates the rise over the run. This represents the change in the y-value divided by the change in the x-value between two distinct points on the line. Considering this, the correct choice for calculating the slope is a) m = (y2 - y1) / (x2 - x1).
When selecting two points to calculate the slope, it's best to choose points that are far apart to minimize any errors in reading data from the graph. An example of finding the slope with given coordinates would be using the points (6.4 s, 2000 m) and (0.50 s, 525 m), which are on the graph representing a line. Here, the calculations would be as follows: slope (m) = (2000 m - 525 m) / (6.4 s - 0.50 s) = (1475 m) / (5.9 s).