Select one of the pairs of points. For example, the pairs of points might be the pair (1, 2) and (2, 4), and the pair (3, 6) and (4, 8). With this example, select (1, 2) and (2, 4).
Label the first point as (x1, y1) and the second point as (x2, y2). In this example, x1 equals 1, y1 equals 2, x2 equals 2, and y2 equals 4.
Subtract x1 from x2 and y1 from y2, and then divide the y-difference by the x-difference to find the line's slope. In this example, 2 - 1 equals 1, 4 - 2 equals 2, and 2 divided by 1 equals 2.
Substitute the slope calculated from the last step for m in the equation (y - y0) = m * (x - x0). With this example, the equation becomes (y - y0) = 2 * (x - x0).
Substitute one point's x-coordinate for x0 and the same point's y-coordinate for y0 to complete the point-slope form. Concluding this example, selecting the point (4, 8), the equation becomes (y - 8) = 2 * (x - 4).