我来回答：1.原式=[(x-1)-(x+1)]/[(x-1)(x+1)]•(x-1)/(-2)=-2/[(x-1)(x+1)]•(x-1)/(-2)=1/(x+1)2.原式= 9xˆ4yˆ4÷x²yˆ-4 •(-x³)=-9xˆ(4-2+3)yˆ4+4=-9xˆ5...