x²-y²=（x+y)(x-y)=6x+y-2=0∴x+y=2∴x-y=6/(x+y)=6/2=3x+y=2 (1)x-y=3 (2)解方程组得 x=5/2, y= -1/23x-y-5=15/2-(-1/2)-5=15/2+1/2-5=8-5=3
