已知2分之a=3分之b=4分之c求(a-b-c分之a*2-ab+ac)÷(2分之a-b+c)的值

解： 令a/2=3/b=c/4=t，则a=2t b=3t c=4t [(a²-ab+ac)/(a-b-c)]÷[(a-b+c)/2] =[(4t²-6t²+8t²)/(2t-3t-4t)]/[(2t-3t+4t)/2] =[6t²/(-5t)]/(3t/2) =(-6t/5)/(3t/2) =(-6/5)(2/3)