是不是题写错了?没有对的啊
a^2/(a^(-1))=a^(2-(-1))=a^3
a^3+a^3=2a^2
a^3*(a^3)=a^(3+3)=a^6
a^4-a^4=0
A
(-x+y)(x-y)=-(x-y)(x-y)=-(x-y)^2