化简[(a-2)/(a*a+2a)-(a-1)/(a*a+4a+4)]/[(a-4)/(a+2)]={(a-2)/[a(a+2)]-(a-1)/(a+2)²} ×[(a+2)/(a-4)]=[(a²-4)-a(a-1)]/[a(a+2)²] ×[(a+2)/(a-4)]=(a-4)/[a(a+2)²]×(a+2)/(a-4)=1/[(a(a+2)...