[(3-a+1)/(a+1)]/[(a方-4a+4)/(a+1)]=[(3-a+1)/(a+1)]/[(a-2)方/(a+1)]=[(3-a+1)/(a+1)]*[(a+1)/(a-2)方]=(3-a+1)*[1/(a-2)方]=(3-0+1)*[1/(0-2)方]=4*(1/4)=1 注:a+1和a-2作为分母都不能等于0,所以a不能取-1和2,只...