∵| 3-y | + | x+y | =0 又∵| 3-y |≥0| x+y |≥0∴| 3-y |=0 y=3 ∴ | x+y |=0x+y=0x= -y = -3x+y/xy= -3+3/（-9）= -3-1/3= -3又1/3 = -10/3