x-y+1=0
y=x+1
代入xy-2x-2y-7=0
得x(x+1)-2x-2(x+1)-7=0
x1=(3+3√5)/2,x2=(3-3√5)/2
y1=(5+3√5)/2,y2=(5-3√5)/2
x^2+y^2=31+12√5
或31-12√5
4x2y2-x4-y4=-(x^2-y^2)^2
-(x^2-y^2)^2=-61+24√5
或-61-24√5额，为什么你们的答案不一样？已知x-y+1=0(1)xy-2x-2y-7=0(2)x=y-1则y(y-1)-2(y-1)-2y-7=0y^2-y-2y+2-2y-7=0y^2-4y-5=0（算错）应是y^2-5y-5=0