(-x)^7/(-x)^3=(-x)^(7-3)=(-x)^4 =x^4
a^m+2/a^m-1=[1/(a^m)+1]^2-2
(a^3)^5/(-a^2)^4/a^2=a^15 / [a^(8+2)]=a^15/a^10=a^5
(-1/2)^3/(-1/2)^5=1/[(-1/2)^2]=1/(1/4)=4
(-3)^0/(-3)^-1=1/(-1/3)=-3
(a^2*a^4)^3/(-a^3)^2/a=a^[(2+4)x3]/a^6/a=a^(12+1)=a^13