①[(x+y)^2-(x+y)(x-y)]/2y=[(x+y)(x+y-x+y)]/2y=[(x+y)*2y]/2y=x+y②（-1/3a^3b^2)^2(-2ab^2)^3/(1/9a^4b^4)^2=(1/9a^6b^4)(-8a^3b^6)/(1/81a^8b^8)=(-8/9a^9b^10) /(1/81a^8b^8)=-72ab^2