The slope on a graph
The slope of the line tells us the rate of change of y relative to x. The slope of a line can be calculated with only two points from the line, (x1, y1) and (x2, y2). The slope of a line characterises the direction of a line. The greater the slope, the steeper the line. The slope is represented by the letter m.
The equation used to calculate the slope from two points is:

There three steps invovled in calculating the slope of a straight line when the equation is not given is.
Step 1: Identify two points on the line.
Step 2: Select one to be (x1, y1) and the other to be (x2, y2).
Step 3: Use the slope equation to calculate slope.