1) -5(x+y)(y-x) 2) -10y(2y+3z)(3z-2y) 3)-10x(0.8y+05x^2)(0.5x^2-0.8y)

1) -5(x+y)(y-x) =-5(x+y)(-(x-у)) =5(х+у)(х-у)=5(x^2-y^2)=5x^2-5y^2 2) -10y(2y+3z)(3z-2y) =-10y(2y+3z)(-(2y-3z)) =10y(2y+3x)(2y-3x)=10y(4y^2-9z^2)=40y^3-90yz^2 3)-10x(0.8y+0.5x^2)(0.5x^2-0.8y)=-10x(0.8y+0.5x^2)(-(0.8y-0.5x^2))=10x(0.8y+0.5x^2)(0.8y-0.5x^2)=10x(0.64y^2-0.25x^4)=6.4xy^2-2.5x^5