x-y=6,x+y=6.则x=6,y=o
xy=0,
0-6=-6两数之和与两数之差都为6,应为两数之和与两数之商都为六x+y=6,x/y=6则x=6y,6y+y=6即y=6/7x=36/7xy=216/49-(36/7-6/7)=216/49-30/7=6/49