x*x+2x-y*y+6y-8=0,x+y不等于2,求x-y的值
问题描述:
x*x+2x-y*y+6y-8=0,x+y不等于2,求x-y的值
答
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