m/1-m²=m/[(1-m)(1+m)]
　　x²+2x+1/x²+x=(x+1)²/x(x+1)=(x+1)/x
　　3x-6/x²-4x+4=3(x-2)/(x-2)²=3/(x-2)若y/1-y=A/y-1=y²/B=C/1-y² 则A BC各等于，就这一题若y/1-y=A/y-1=y²/B=C/1-y²
若y（1+y）/1-y² =(y+y² )/(1-y² )=-A(1+y)/(1-y² )=y²(1-y² )/(1-y² )B=C/(1-y² )