Find the product (2xy - y)(3x^{2} + 7xy).

Using FOIL, we find

(2xy)(3x^{2}) + (2xy)(7xy) + (-y)(3x^{2}) + (-y)(7xy)

This simplifies to

6x^{3}y + 14x^{2}y^{2} - 3x^{2}y - 7xy^{2}