(1)
(2x-3y)^2-2(2x-3y)(2y-3x)
=(2x-3y)(2x-3y-4y+6x)
=(2x-3y)(8x-7y)
=(4024-6039)(16096-14091)
=-2015×2005
=-4040075
(2)=x^2-4 +xy-2y
=(x+2)(x-2)+y(x-2)
=(x-2)(x+2+y)