9a平方-1/a平方+2a *a+2/1-3a /1/5a=(3a-1)(3a+1)/a(a+2)*(a+2)/(1-3a )*5a=-5(3a+1)4-x平方/x平方+4x+4/x-2/2x+4*x-1/2 =(2-x)(x+2)/(x+2)^2/(x-2)/2(x+2)*(x-1)/2=(2-x)(x+2)/(x+2)^2*2(x+2)/(x-2)*(x-1)/2=x-1-（...