通分：
1/﹙x²-x﹚=(x+1)^2/x(x-1)(x+1)^2,
1/﹙x²+x﹚=(x-1)(x+1)/x(x-1)(x+1)^2
1/﹙x+1﹚² =x(x-1)/x(x-1)(x+1)^2
约分:﹙m³+2m²+m﹚/﹙m²-1﹚=m(m+1)^2/(m+1)(m-1)=m(m+1)/(m-1)