Here the product is calculated in the following manner:

We multiply the terms on the x axis (horizontal)and y axis(vertical).

For example, when -2y² is on the X axis (observe the 1^st row 3^rd column) and 3x is on the Y axis(2^nd row 1^st column) then ,the product

becomes -2y²×3x = -6xy²(observe the 2^nd row 3^rd column).