x-y=1,xy=3,xy是什么?

x-y=1,

x=y+1

xy=3

(y+1)y=3

y^2+y-3=0

y^2+y+1/4-1/4-3=0

(y+1/2)^2-13/4=0

(y+1/2-√13/2)(y+1/2+√13/2)=0

y=-1/2+√13/2或y=-1/2-√13/2

当y=-1/2+√13/2时,

x=y+1=-1/2+√13/2+1=1/2+√13/2

当y=-1/2-√13/2时,

x=y+1=-1/2-√13/2+1=1/2-√13/2

所以x=1/2-√13/2,y=-1/2-√13/2或x=1/2+√13/2,y=-1/2+√13/2