x²+2x-y²+6y-8=0x²+2x+1-(y²-6y+9)=0(x+1)²-(y-3)²=0(x+1)²=(y-3)²x+1=±(y-3)x+1=y-3x-y=-4 x+1=-(y-3)x+y=2(舍) ∴x-y=-4