1. -x^3*(-x)^5+x^4*(-x)^4
=(-x^3)*(-x)^5+x^4*x^4
=x^8+x^8
=2x^8
2.27*3^m*3^m-2
=3^3*3^m*3^m-2
=3^(3+m+m-2)
=3^(2m+1)
3.(-1)^2m+1*(-1)^2m
=1^m+1^m
=1+1
=2
4.(x+y)^3*(-x-y)^4*(-y-x)^3
=(x+y)^3*(x+y)^4*-(x+y)^3
=-(x+y)^10