1.(x-y)^2*(x-y)^3*(y-x)^2*(y-x)^3
=-(x-y)^2*(x-y)^3*(x-y)^2*(x-y)^3
=-(x-y)^(2+3+2+3)
=-(x-y)^10
2.(-x)^2*(-x)^3+2x*(-x)^4-(-x)*x^4
=x^2*(-x)^3+2x^5+x^5
=-x^5+3x^5
=2x^5
3.x*x^m-1+x^2*x^m-2-3*x^3*x^m-3
=x^m+x^m-3x^m
=-x^m
4..(a-b-c)*(b+c-a)^2*(c-a+b)^3
=-(a-b-c)*(a-b-c)^2*(a-b-c)^3
=-(a-b-c)^6