Is the horizontal change the differences in the x-coordinates when computing slope?
When computing the slope of a line, choose two points along the
line and do the following:
Let's say the points we choose are (1,3) & (2,5). To compute
the slope we need to use the slope formula: m = (y1-y2) / (x1-x2).
So, using the two points we chose, just plug them into the formula:
m = (3-5) / (1-2) = -2 / -1 = 2. Therefore, our slope is 2. These
particular points yield the graph, y = 2x + 1.