How you use this: first you write down the two binomials that are multiplying each other and put one of the binomials to the bottom so that you can make a table. The white one represent negatives and the shaded one represent positives. The second step is to draw down the binomials and trace a long straight line from the end each of the drawings so that it could cross with the other line of the binomial. After that write down in light form of the middle one.