256x254/255+254x1/255=(255+1)x254/255+(255-1)x1/255=255x254/255+254/255+255x1/255-1/255=254+254/255+1-1/255=255+253/255=255又253/255 （1046+4/5+5/6+6/7）÷(4/5+5/6+6/7)=[2x210x（4/5+5/6+6/7）+(4/5+5/6...