-10ху-15у^2+2х^2+3ху=-7ху-15у^2+2х^2
(5y-x)(-2x-3y)=-5y*2x-5y*3y-x*(-2x)-x*(-3y)=-10xy-15y^2+2x^2+3xy=-7xy-15y^2+2x^2
-10ху-15у^2+2х^2+3ху=-7ху-15у^2+2х^2
(5y-x)(-2x-3y)=-5y*2x-5y*3y-x*(-2x)-x*(-3y)=-10xy-15y^2+2x^2+3xy=-7xy-15y^2+2x^2